Semiconductor light emitting device including a fluorescent material

ABSTRACT

A semiconductor light emitting element, semiconductor light emitting device or image display device includes a wavelength converter for converting a wavelength into another, optical reflector having a wavelength selectivity and a light absorber having a wavelength selectivity, which are disposed in a predetermined positional relation, to prevent external leakage of primary light and to extract secondary light made by wavelength-converting the primary light with a very high efficiency. By using a semiconductor light emitting element for ultraviolet emission, or by combining it with a fluorescent material or any other appropriate material having a wavelength converting function, various kinds of applications, such as illuminator, having a remarkably long-life light source can be made. The semiconductor light emitting element preferably has a emission wavelength near 330 nm, and preferably uses BGaN in its light emitting layer. These light emitting element and device are stable in emission wavelength and can be readily configured for highly efficient wavelength conversion of any wavelength in a wide wavelength range from the visible light band to the infrared band. They can be used in various kinds of devices and instruments requiring a light source to simplify their structures, decreasing their sizes and weights, stabilize their emission wavelengths and quantities of light and elongate their lives.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a semiconductor light emitting element,semiconductor light emitting device, image display device, and so on.More specifically, the invention relates to a semiconductor lightemitting element, semiconductor light emitting device, image displaydevice, and any other elements and devices configured to preventexternal leakage of primary light emitted from a light emitting layerand to thereby waveform-convert it into secondary light and extract itwith a remarkably high efficiency.

[0002] Semiconductor light emitting elements and various types ofsemiconductor light emitting devices using same have various advantages,such as compactness, low power consumption and high reliability, and areused in progressively wider applications, such as indoor and outdoordisplay panels, railway and traffic signals, car-borne signalilluminators, which are required to be highly luminous and highlyreliable.

[0003] Among these semiconductor light emitting elements, those usinggallium nitride compound semiconductors are being remarked recently.Gallium nitride compound semiconductors are direct-transitional III-Vcompound semiconductors which can efficiently emit light in relativelyshort wavelength ranges.

[0004] Throughout the present application, the “gallium nitride compoundsemiconductor” pertain to III-V compound semiconductors expressed byB_(x)In_(y)Al_(z)Ga_((1-x-y-z))N (0≦x≦1, 0≦y≦1, 0≦z≦1) and to any mixedcrystal which includes phosphorus (P) or arsenic (As), for example, asgroup V species in addition to N in the above-mentioned chemicalformula.

[0005] Gallium nitride compound semiconductors are remarked as hopefulmaterials of LEDs (light emitting diodes) and semiconductor lasersbecause the band gap can be changed from 1.89 to 6.2 eV by controllingthe mole fractions x, y and z in the above-mentioned chemical formula.If highly luminous emission is realized in short wavelength ranges ofblue and ultraviolet, the recording capacities of all kinds of opticaldiscs may be doubled, and full color images will be realized on displaydevices. Under such and other prospects, short wavelength light emittingelements using gallium nitride compound semiconductors are under rapiddevelopments toward improvements in their initial characteristics andreliability.

[0006] Structures of conventional light emitting elements using galliumnitride compound semiconductors are disclosed in, for example, Jpn. J.Appl. Phys., 28 (1989) p.L2112; Jpn. J. Appl. Phys., 32(1993) p.L8; andJapanese Patent Laid-Open Publication No. 5-291621.

[0007]FIG. 141 is a cross-sectional view schematically showing aconventional semiconductor light emitting element. The semiconductorlight emitting element 6100 shown here is a gallium nitridesemiconductor light emitting element. The light emitting element 6100has a multi-layered structure of semiconductors stacked on a sapphiresubstrate 6120, namely, a buffer layer 6114, n-type contact layer 6160,n-type cladding layer 6140, light emitting layer 6120, p-type claddinglayer 6122 and p-type contact layer 6124 which are stacked in this orderon the sapphire substrate 6120.

[0008] The buffer layer 6140 may be made of n-type GaN, for example. Then-type contact layer 6160 has a high n-type carrier concentration toensure ohmic contact Myth the n-side electrode 6134, and its materialmay be GaN, for example. The n-type cladding layer 6118 and the p-typecladding layer 6122 function to confine carriers within the lightemitting layer 6120, and their refractive index must be lower than thatof the light emitting layer 6120. The light emitting layer 6120 is alayer in which emission occurs due to recombination of electric chargesinjected as a current into the light emitting element.

[0009] The light emitting layer 6120 may be made of undoped InGaN, forexample, and the cladding layers 6118 and 6122 may be made of AlGaNhaving a larger band gap than the light emitting layer 6120. The p-typecontact layer 6124 has a high p-type carrier concentration to ensureohmic contact with the p-side electrode 6126, and its material may beGaN, for example.

[0010] Stacked on the p-type contact layer 6124 is the p-side electrode6126 which is transparent to the emitted light. Stacked on the n-typecontact layer 6160 is the n-side electrode 6134. Bonding pads 6132 of Auare stacked on these electrodes, respectively, so that wires (not shown)for supplying a operating current to the-element be bonded. The surfaceof the element is covered by the protective films 6130 and 6145 ofsilicon oxide, for example.

[0011] The conventional light emitting element 6100 is so configuredthat light emitted from the light emitting layer be directly extractedexternally, and involved the problems indicated below.

[0012] One of the problems lies in variable emission wavelengths causedby structural varieties of light emitting elements. That is,semiconductor light emitting elements, even when manufactured under thesame conditions, are liable to vary in quantity of impurities and inthicknesses of respective layers, which results in variety in emissionwavelength.

[0013] Another problem lies in changes in emission wavelength dependingupon the operating current. That is, emission wavelength of asemiconductor light emitting element may change depending upon thequantity of electric current supplied thereto, and it was difficult tocontrol the emission luminance and emission wavelength independently.

[0014] Another problem lies in changes in emission wavelength dependingupon the temperature. That is, when the temperature of a semiconductorlight emitting element, particularly of its light emitting layer,changes, the effective band gap of the light emitting layer alsochanges, and causes an instablility of the emission wavelength.

[0015] As explained above, in conventional semiconductor light emittingelements, it was difficult to entirely control varieties in structure,temperature and electric current and to thereby limit changes inemission wavelength within a predetermined range, such as severalnm(nanometers).

[0016] Conventional semiconductor light emitting devices involved anadditional problem, namely, materials and structures of semiconductorlight emitting elements used therein had to be determined and changedappropriately in accordance with desired emission wavelengths, such asselecting AlGaAs materials for emission of red light, GaAsP or InGaAlPmaterials for yellow light, GaP or InGaAlP materials for green light andInGaN materials for blue light.

SUMMARY OF THE INVENTION

[0017] It is therefore an object of the invention to provide asemiconductor light emitting element and a semiconductor light emittingdevice which are highly stable in emission wavelength and canwavelength-convert light with a high conversion efficiency in a widewavelength range from visible light to infrared band.

[0018] According to the first aspect of the invention, there is provideda semiconductor light emitting element and a light emitting devicecomprising a wavelength converter located adjacent to a light extractionend of the light emitting layer to absorb the primary light emitted fromthe light emitting layer and to release secondary light of a secondwavelength different from the first wavelength.

[0019] The first aspect of the present invention is embodied in theabove-mentioned mode, and attains the effects explained below.

[0020] Light from the light emitting layer is not extracted directly butconverted in wavelength by a fluorescent material. Therefore, it isprevented that the emission wavelength varies with varieties ofmanufacturing parameters of the semiconductor light emitting elements,drive current, temperature and other inevitable factors. That is, theinvention realizes remarkable stability of emission wavelengths andmakes it possible to control the emission luminance and the emissionwavelength independently.

[0021] The fluorescent material may include a plurality of differentmaterials to obtain a plurality of different emission wavelengths. Forexample, by appropriately mixing different fluorescent materials for red(R), green (G) and blue (B) to form the fluorescent material in eachlight emitting element, emission of white light can be obtained easily.

[0022] The material and the structure of the semiconductor lightemitting elements used in a device need not be changed depending on thedesired emission wavelength of the device. That is, in conventionaltechniques, optimum materials had to be selected to form semiconductorlight emitting elements in accordance with desired emission wavelengths,such as selecting AlGaAs materials for emission of red light, GaPmaterials for yellow light, InGaAlP materials for green light and InGaNmaterials for blue light. However, according to the invention, it issufficient to select appropriate fluorescent materials, and the materialof the semiconductor light emitting element need not be changed.

[0023] Even when a device needs an arrangement of a plurality ofsemiconductor light emitting elements having different emission colors,such elements for different emission colors can be made only by changingthe material of the fluorescent member, and all of the semiconductorlight emitting elements may be common in materials and structure. Thiscontributes to simplification of the structure of the light emittingdevice, remarkable reduction of the manufacturing cost and higherreliability. Additionally, by uniforming the drive current, suppliedvoltage or the size of the elements, its application can be extendedremarkably.

[0024] According to the second aspect of the invention, there isprovided a semiconductor light emitting element, a light emitting deviceand a image display device comprising a light emitting layer foremitting primary light of a first wavelength, a wavelength converterlocated adjacent to a light extraction end of the light emitting layerto absorb the primary light emitted from the light emitting layer and torelease secondary light of a second wavelength different from the firstwavelength, and a first optical reflector located adjacent to a lightrelease end of the wavelength converter and having a lower reflectancefor the secondary light released from the wavelength converter and ahigher reflectance for the primary light passing through the wavelengthconverter.

[0025] Since the optical reflector RE1 is provided, the primary lighthaving leaked through the wavelength converter FL can be reflected witha high efficiency and can be returned back to the wavelength converterFL. The primary light returned back in this manner iswavelength-converted by the wavelength converter FL, and passes throughthe optical reflector RE1 as secondary light. That is, the opticalreflector RE1 located adjacent to the emission end of the wavelengthconverter FL prevents leakage of primary light by returning part of theprimary light passing through the wavelength converter FL back to it forwavelength conversion thereby. Therefore, the primary light can bewavelength-converted with a high efficiency. Additionally, thewavelength converter FL is prevented from being exited by outerturbulent light and from emitting undesired light.

[0026] The semiconductor light emitting element may include an opticalabsorber AB. In this case, the optical absorber absorbs primary lightpassing through the optical reflector RE1 and prevents external leakagethereof. The light absorber AB also functions to adjust the spectrum ofthe extracted light and to improve the chromatic pureness. Additionally,since the Light absorber AB absorbs ultraviolet rays entering from theexterior, it is prevented that such external turbulent light undesirablyexcites the wavelength converter FL and causes undesired emission.

[0027] The semiconductor light emitting element may further include areflector RE2 to reflect primary light back into the wavelengthconverter FL. As a result, primary light can be wavelength-converted andextracted with a higher efficiency.

[0028] The semiconductor light emitting element may further includes anoptical reflector RE3 for greater improvement of the wavelengthconversion efficiency. In this case, not only the primary light but alsothe secondary light or any other optical component different inwavelength from the primary light can be prevented from externalleakage. The optical reflector RE3 has a limitative aperture so thatlight can exit only through the aperture. By decreasing the size of theaperture, a light emitting element as a point-sized light source can bemade easily. Such a point-sized light source enables effectivecollection of light by lenses or other optical elements, and it istherefore practically advantageous in most cases.

[0029] The semiconductor light emitting element may further include anoptical reflector RE4 to more efficiently extract secondary light byreflecting it after wavelength conversion by the wavelength converterFL.

[0030] According to the invention, it is also possible to realize animage display device with a low power consumption, long life, highreliability, quick rising and good mechanical reliability.

[0031] As explained above, the invention provides a semiconductor lightemitting element, semiconductor light emitting device and image displaydevice which are simple in structure, stable in emission wavelength,excellent in emission efficiency, and capable of highly luminousemission in a wide wavelength range from visible light to infraredbands, and the invention promises great industrial contribution.

[0032] Moreover, the invention can provide various applications of thesemiconductor light emitting element or device, such as illuminators,which are more efficient, lower in power consumption and longer in lifethan conventional fluorescent lamps and bulbs.

[0033] The illuminator according to the invention comprises: asemiconductor light emitting element for emitting ultraviolet rays; anda fluorescent element for absorbing said ultraviolet rays emitted fromsaid semiconductor light emitting element and for releasing secondarylight having a longer wavelength than said ultraviolet rays.

[0034] Said semiconductor light emitting element preferably containsgallium nitride compound semiconductor in a light emitting layerthereof.

[0035] Preferably, said secondary light is substantially a visiblelight.

[0036] Preferably, a predetermined number of said semiconductor lightemitting elements are serially connected to form a unit, and a pluralityof said units are connected in parallel.

[0037] The illuminator preferably further comprises a converter circuitfor converting a high frequency voltage into a d.c voltage so that saidsemiconductor light emitting elements be driven when connected to apower source of a fluorescent lamp.

[0038] The illuminator preferably further comprises a first opticalreflection film located between said semiconductor light emittingelement and said fluorescent element, and having a wavelengthselectivity to pass said ultraviolet rays and to reflect said secondarylight released from said fluorescent element.

[0039] The illuminator preferably further comprises a second opticalreflection film located on one side of said fluorescent element oppositefrom said semiconductor light emitting element, and having a wavelengthselectivity to reflect said ultraviolet rays and to pass said secondarylight released from said fluorescent element.

[0040] The illuminator preferably further comprises a light absorberlocated on one side of said fluorescent element opposite from saidsemiconductor light emitting element, and having a wavelengthselectivity to absorb said ultraviolet rays and to pass said secondarylight released from said fluorescent element.

[0041] The illuminator preferably comprises a firing board; lightemitting devices supported on said wiring board; and a translucent outershell encapsulating said wiring board, each said semiconductor lightemitting device including: said semiconductor light emitting element;and said fluorescent element.

[0042] The illuminator preferably comprises a wiring board; a pluralityof semiconductor light emitting elements supported on said wiringboards; and a translucent outer shell encapsulating said wiring board,said outer shell having a fluorescent element on the inner wall surfacethereof.

[0043] The illuminator preferably further comprises a pulse generatorfor supplying a pulsating operating current to said semiconductor lightemitting element.

[0044] The illuminator preferably further comprises a concave mirror forreflecting said visible light to orient it in a predetermined direction.

[0045] Preferably, the emission wavelength of said semiconductor lightemitting element is approximately 330 nm.

[0046] A read-out device according to the invention comprises: asemiconductor light emitting element for emitting ultraviolet rays; afluorescent element for absorbing said ultraviolet rays emitted fromsaid semiconductor light emitting element and for releasing light havinga longer wavelength than said ultraviolet rays; and a photodetector fordetecting said light with the longer wavelength reflected in theexterior, said light emitted released from said fluorescent elementbeing irradiated onto a manuscript to read out information therefrom.

[0047] Preferably, said semiconductor light emitting element contains agallium nitride compound semiconductor in a light emitting layerthereof.

[0048] A projector according to the invention for projecting a profileon a translucent medium in an enlarged scale, comprises: a semiconductorlight emitting element for emitting ultraviolet rays; a fluorescentelement for absorbing said ultraviolet rays emitted from saidsemiconductor light emitting element and for releasing visible light;and an optical system for collecting said visible light to direct itonto a screen.

[0049] Preferably, said semiconductor light emitting element contains agallium nitride compound semiconductor in a light emitting layerthereof.

[0050] A purifier according to the invention comprises: a purifyingcircuit for passing a liquid or a as therethrough; and a semiconductorlight emitting element located along said purifying circuit to emitultraviolet rays.

[0051] Preferably, said semiconductor light emitting element contains agallium nitride compound semiconductor in a light emitting layerthereof.

[0052] The purifier preferably further comprises an ozone generatoralong said purifying circuit so that said ultraviolet rays areirradiated to a liquid containing ozone generated by said ozonegenerator.

[0053] The purifier preferably further comprises a heater along saidpurifying circuit a gas purified by said purifying circuit be dischargedafter being heated.

[0054] Preferably-the emission wavelength of said semiconductor lightemitting element is approximately 330 nm.

[0055] A display device according to the invention comprises: asemiconductor light emitting element for releasing ultraviolet rays; anda display panel having stacked a fluorescent element for absorbing saidultraviolet rays released from said semiconductor light emitting elementand for releasing visible light.

[0056] Preferably, said semiconductor light emitting element contains agallium nitride compound semiconductor in a light emitting layerthereof.

[0057] Illuminators according to the invention have high mechanicalstrengths against impulses or vibrations.

[0058] Light from the light emitting layer is not extracted directly butconverted in wavelength by a fluorescent material. Therefore, it isprevented that the emission wavelength varies with varieties ofmanufacturing parameters of the semiconductor light emitting elements,drive current, temperature and other inevitable factors. That is, theinvention realizes remarkable stability of emission wavelengths andmakes it possible to control the emission luminance and the emissionwavelength independently.

[0059] The fluorescent material may include a plurality of differentmaterials to obtain a plurality of different emission wavelengths. Forexample, by appropriately mixing different fluorescent materials for red(R), green (G) and blue (B) to form the fluorescent material in eachlight emitting element, emission of white light can be obtained easily.

[0060] The light emitting layer may be made of GaN containing boron. Inthis case, ultraviolet rays near 330 nm which efficiently excites thefluorescent member can be obtained and enhanced.

[0061] Efficiency of the wavelength conversion can be enhanced to moreeffectively extract the secondary light by reflecting and confiningultraviolet rays emitted from the semiconductor light emitting elementand by reflecting and externally guiding the secondary light emittedfrom the fluorescent member.

[0062] The material and the structure of the semiconductor lightemitting elements used in a device need not be changed depending on thedesired emission wavelength of the device. That is, in conventionaltechniques, optimum materials had to be selected to form semiconductorlight emitting elements in accordance with desired emission wavelengths,such as selecting AlGa materials for emission of red light, GaAsPmaterials for yellow light, InGaAlP or GaP materials for green light andInGaN materials for blue light. However, according to the invention, itis sufficient to select appropriate fluorescent materials, and thematerial of the semiconductor light emitting element need not bechanced.

[0063] Even when a device needs an arrangement of a plurality ofsemiconductor light emitting elements having different emission colors,such elements for different emission colors can be made only by changingthe material of the fluorescent member, and all of the semiconductorlight emitting elements may be common in materials and structure. Thiscontributes to simplification of the structure of the light emittingdevice, remarkable reduction of the manufacturing cost and higherreliability. Additionally, by uniforming the drive current, suppliedvoltage or the size of the elements, its application can be extendedremarkably.

[0064] As explained above, the invention provides an illuminator andother various kind of applications which are simple in structure, stablein emission wavelength, and capable of highly luminous emission in awide wavelength range from visible light to infrared bands, and theinvention promises great industrial contribution.

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The present invention will be understood more fully from thedetailed description given hereinbelow and from the accompanyingdrawings of the preferred embodiments of the invention. However, thedrawings are not intended to imply limitation of the invention to aspecific embodiment, but are for explanation and understanding only.

[0066] In the drawings:

[0067]FIG. 1 is a cross-sectional view schematically showing asemiconductor light emitting element taken as the first embodiment ofthe invention,

[0068]FIG. 2 is a cross-sectional view schematically showing the secondsemiconductor light emitting element of the invention,

[0069]FIG. 3 is a roughly illustrated cross-sectional view of a lightemitting device according to the invention,

[0070]FIG. 4 is a roughly illustrated cross-sectional view of a lightemitting device according to the invention,

[0071]FIG. 5 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the invention,

[0072]FIG. 6 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the invention,

[0073]FIG. 7 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the invention,

[0074]FIG. 8 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the invention,

[0075]FIG. 9A is a roughly illustrated plan view and

[0076]FIG. 9B is a roughly illustrated cross-sectional view of a seventhexample of the light emitting device according to the invention,

[0077]FIG. 10A through 10D are roughly illustrated views of the eighthexample of the light emitting devices according to the invention,

[0078]FIG. 10A is a perspective view and

[0079]FIG. 10B is a partially enlarged perspective view in a partiallysee-through mode, and the substrate type includes a cavity type as shownin

[0080]FIG. 10C as the cross sectional view and a resin mold type asshown in

[0081]FIG. 10D as the cross sectional view,

[0082]FIG. 11 is a roughly illustrated cross sectional view of the ninthexample of the light emitting device according to the invention,

[0083]FIG. 12A is a roughly illustrated plan view and

[0084]FIG. 12B is a roughly illustrated cross-sectional view of a tenthexample of the light emitting device according to the invention,

[0085]FIG. 13A is a roughly illustrated perspective view and

[0086]FIG. 13B is a roughly illustrated cross-sectional view of aeleventh example of the light emitting device according to theinvention,

[0087]FIG. 14 is a roughly illustrated perspective view of a twelfthexample of the light emitting device according to the invention,

[0088]FIG. 15 is a roughly illustrated cross sectional view of athirtieth example of the light emitting device according to theinvention,

[0089]FIG. 16 is a roughly illustrated cross sectional view of a exampleof the light emitting device according to the embodiment,

[0090]FIG. 17 is a roughly illustrated cross-sectional view of a lightemitting device according to the invention,

[0091]FIG. 18 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the invention,

[0092]FIG. 19 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the invention,

[0093]FIG. 20 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the invention,

[0094]FIG. 21 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the invention,

[0095]FIG. 22A is a roughly illustrated plan view and

[0096]FIG. 22B is a roughly illustrated cross-sectional view of aseventh example of the light emitting device according to the invention,

[0097]FIG. 23A and 23B are roughly illustrated cross sectional views ofthe eighth example of the light emitting devices according to theinvention,

[0098]FIG. 24 is a roughly illustrated cross sectional view of the ninthexample of the light emitting device according to the invention,

[0099]FIG. 25 is a roughly illustrated cross-sectional view of a tenthexample of the light emitting device according to the invention,

[0100]FIG. 26 is a roughly illustrated cross sectional view of aeleventh example of the light emitting device according to theinvention,

[0101]FIG. 27A through 27C are a roughly illustrated cross sectionalview of a example of the light emitting device according to theembodiment,

[0102]FIG. 28A through 28C are roughly illustrated cross-sectional viewsof a second examples of the light emitting device according to theembodiment,

[0103]FIG. 29A through 29C are roughly illustrated cross-sectional viewsof third examples of the light emitting device according to theembodiment,

[0104]FIG. 30A through 30C are roughly illustrated cross-sectional viewsof a forth examples of the light emitting device according to theembodiment,

[0105]FIG. 31A through 31C are roughly illustrated cross-sectional viewsof fifth examples of the light emitting device according to theembodiment,

[0106]FIG. 32A through 32C are roughly illustrated cross-sectional viewsof the sixth examples of the light emitting devices according to theembodiment,

[0107]FIG. 33A through 33C are roughly illustrated cross-sectional viewsof the seventh examples of the light emitting device according to theembodiment,

[0108]FIG. 34A through 34C are roughly illustrated cross-sectional viewsof eighth examples of the light emitting device according to theembodiment,

[0109]FIG. 35 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment,

[0110]FIG. 36 is a roughly illustrated cross-sectional view of a lightemitting device according to the embodiment,

[0111]FIG. 37 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment,

[0112]FIG. 38 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment,

[0113]FIG. 39 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment,

[0114]FIG. 40 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment,

[0115]FIG. 41 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment,

[0116]FIG. 42 is a roughly illustrated cross-sectional view of a lightemitting device according to the embodiment,

[0117]FIG. 43 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment,

[0118]FIG. 44 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment,

[0119]FIG. 45 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment,

[0120]FIG. 46 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment,

[0121]FIG. 47 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment,

[0122]FIG. 48 is a roughly illustrated cross-sectional view of a lightemitting device according to the embodiment,

[0123]FIG. 49 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment,

[0124]FIG. 50 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment,

[0125]FIG. 51 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment,

[0126]FIG. 52 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment,

[0127]FIG. 53 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment,

[0128]FIG. 54 is a roughly illustrated cross-sectional view of a lightemitting device according to the embodiment,

[0129]FIG. 55 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment,

[0130]FIG. 56 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment,

[0131]FIG. 57 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment,

[0132]FIG. 58 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment,

[0133]FIGS. 59A and 59B are a roughly illustrated view and across-sectional view of a seventh example of the light emitting deviceaccording to the embodiment respectively,

[0134]FIG. 60 is a roughly illustrated cross-sectional view of a eighthexample of the light emitting device according to the embodiment,

[0135]FIG. 61 is a roughly illustrated cross-sectional view of a ninthexample of the light emitting device according to the embodiment,

[0136]FIG. 62 is a roughly illustrated cross-sectional view of a tenthexample of the light emitting device according to the embodiment,

[0137]FIG. 63 is a roughly illustrated cross-sectional view of aeleventh example of the light emitting device according to theembodiment,

[0138]FIG. 64 is a roughly illustrated cross-sectional view of a twelfthexample of the light emitting device according to the embodiment,

[0139]FIG. 65 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment,

[0140]FIG. 66 is a roughly illustrated cross-sectional view of a lightemitting device according to the embodiment,

[0141]FIG. 67 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment,

[0142]FIG. 68 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment,

[0143]FIG. 69 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment,

[0144]FIG. 70 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment,

[0145]FIGS. 71A and 71B are a roughly illustrated plan view and across-sectional view of a seventh example of the light emitting deviceaccording to the embodiment respectively,

[0146]FIG. 72 is a roughly illustrated cross-sectional view of a eighthexample of the light emitting device according to the embodiment,

[0147]FIG. 73 is a roughly illustrated cross-sectional view of a ninthexample of the light emitting device according to the embodiment,

[0148]FIG. 74 is a roughly illustrated cross-sectional view of a tenthexample of the light emitting device according to the embodiment,

[0149]FIG. 75 is a roughly illustrated cross-sectional view of aeleventh example of the light emitting device according to theembodiment,

[0150]FIG. 76 is a roughly illustrated cross-sectional view of a twelfthexample of the light emitting device according to the embodiment,

[0151]FIG. 77 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment,

[0152]FIG. 78 is a roughly illustrated cross-sectional view of a lightemitting device according to the embodiment,

[0153]FIG. 79 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment,

[0154]FIG. 80 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment,

[0155]FIG. 81 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment,

[0156]FIG. 82 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment,

[0157]FIGS. 83A and 83B are a roughly illustrated plan view and across-sectional view of a seventh example of the light emitting deviceaccording to the embodiment respectively,

[0158]FIG. 84 is a roughly illustrated cross-sectional view of a eighthexample of the light emitting device according to the embodiment,

[0159]FIG. 85 is a roughly illustrated cross-sectional view of a ninthexample of the light emitting device according to the embodiment,

[0160]FIG. 86 is a roughly illustrated cross-sectional view of a tenthexample of the light emitting device according to the embodiment,

[0161]FIG. 87 is a roughly illustrated cross-sectional view of aeleventh example of the light emitting device according to theembodiment,

[0162]FIG. 88 is a roughly illustrated cross-sectional view of a twelfthexample of the light emitting device according to the embodiment,

[0163]FIGS. 90A and 90B are a roughly illustrated plan view and across-sectional view of a second example of the light emitting deviceaccording to the embodiment respectively,

[0164]FIG. 91 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment,

[0165]FIG. 92 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment,

[0166]FIG. 93 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment,

[0167]FIG. 94 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment,

[0168]FIG. 95 is a roughly illustrated cross-sectional view of a seventhexample of the light emitting device according to the embodiment,

[0169]FIG. 96A is a roughly illustrated cross-sectional view of aexample of the light emitting device according to the embodiment,

[0170]FIG. 96B is a roughly illustrated cross-sectional view of a secondexample of the light emitting device according to the embodiment,

[0171]FIG. 97 is a cross-sectional view schematically showing asemiconductor light emitting element taken as the thirtieth embodimentof the invention,

[0172]FIG. 98 is a cross-sectional view schematically shorting thesemiconductor light emitting element according to the fortiethembodiment,

[0173]FIG. 99 is a cross-sectional view schematically showing thesemiconductor light emitting element according to the fiftiethembodiment,

[0174]FIG. 100 is a cross-sectional view schematically showing thesemiconductor light emitting element according to the sixtiethembodiment,

[0175]FIG. 101 is a cross-sectional view schematically showing thesemiconductor light emitting element according to the seventiethembodiment,

[0176]FIG. 102 is a cross-sectional view schematically showing thesemiconductor light emitting element according to the eightiethembodiment,

[0177]FIG. 103 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention,

[0178]FIG. 104 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention,

[0179]FIG. 105 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention,

[0180]FIG. 106 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention,

[0181]FIG. 107 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention,

[0182]FIG. 108 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention,

[0183]FIG. 109 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention,

[0184]FIG. 110 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention,

[0185]FIG. 111 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention,

[0186]FIG. 112 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention,

[0187]FIG. 113 is a roughly illustrated cross-sectional view of asemiconductor device according to the twenty-ninth embodiment of theinvention,

[0188]FIG. 114 is a cross-sectional schematic view of the secondsemiconductor light emitting device according to the present embodiment,

[0189]FIG. 115 is a cross-sectional schematic view of the thirdsemiconductor light emitting device according to the present embodiment,

[0190]FIG. 116 is a cross-sectional schematic view of the fourthsemiconductor light emitting device according to the present embodiment,

[0191]FIG. 117 is a schematic view of the fifth semiconductor lightemitting device according to the present embodiment,

[0192]FIG. 118 is a schematic view of the sixth semiconductor lightemitting device according to the present embodiment,

[0193]FIG. 119 is a schematic view of the seventh semiconductor lightemitting device according to the present embodiment,

[0194]FIG. 120 is a schematic view of the eighth semiconductor lightemitting device according to the present embodiment,

[0195]FIG. 121 is a schematic cross-sectional view showing thesemiconductor light emitting device according to the thirtiethembodiment of the invention,

[0196]FIG. 122 is a schematic cross-sectional view of the semiconductorlight emitting device according to the thirty-first embodiment,

[0197]FIG. 123 is a schematic cross-sectional view of the semiconductorlight emitting device according to the thirty-second embodiment,

[0198]FIG. 124 is a schematic cross-sectional view of an exemplar)structure of the image display device according to the embodiment,

[0199]FIG. 125 is a schematic cross-sectional view of the modified imagedisplay device according to the thirty-forth embodiment of theinvention,

[0200]FIG. 126A is a perspective view of the entirely of the illuminator4100,

[0201]FIG. 126B is a cross-sectional view, and

[0202]FIG. 126C is a schematic plan view of a showing board usedtherein, and

[0203]FIG. 126D is a schematic diagram showing the electrical circuit ofthe illuminator 4100,

[0204]FIG. 127 is a schematic diagram shorting a conventionalfluorescent lamp system,

[0205]FIG. 128 is a schematic cross-sectional view of a semiconductorlight emitting device 4130 suitable for use in the present embodiment,

[0206]FIG. 129 is a schematic diagram showing a flashing device for acamera according to the invention,

[0207]FIG. 130 is a schematic diagram shorting a lamp according to theinvention,

[0208]FIG. 131 is a schematic diagram showing a read-out deviceaccording to the invention,

[0209]FIG. 132 is a schematic diagram showing a projector according tothe invention,

[0210]FIG. 133 is a schematic diagram showing a purifier according tothe invention,

[0211]FIG. 134 is a schematic diagram of a ultraviolet irradiatoraccording to the seventh embodiment of the invention,

[0212]FIG. 135 is a schematic diagram showing a display device accordingto the invention,

[0213]FIG. 136 is a schematic diagram shorting a semiconductor lightemitting device according to the invention,

[0214]FIG. 137 is a schematic diagram showing a cross-sectional aspectof the semiconductor light emitting element 4132 suitable for use in theinvention,

[0215]FIG. 138 is a graph showing the relation between concentration ofsilicon and photoluminescence (PL) emission intensity when silicon (Si)is doped into BGaN,

[0216]FIG. 139 is a diagram showing a schematic cross-sectional aspectof ultraviolet emission type semiconductor light emitting elementaccording to another embodiment of the invention,

[0217]FIG. 140 is a cross-sectional schematic view showing a modifiedversion of the semiconductor light emitting element 4132B shown in FIG.139, and

[0218]FIG. 141 is a cross-sectional view schematically showing aconventional semiconductor light emitting element.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0219] Explained below some embodiments of the invention fifth referenceto the drawings.

[0220]FIG. 1 is a cross-sectional view schematically showing asemiconductor light emitting element taken as the first embodiment ofthe invention. The semiconductor light emitting element 10 shown here isa gallium nitride semiconductor light emitting element. The lightemitting element 10 has a multi-layered structure of semiconductorsstacked on a sapphire substrate 12, namely, a buffer layer 14, n-typecontact layer 16, n-type cladding layer 18, light emitting layer 20,p-type cladding layer 22 and p-type contact layer 24 which are stackedin this order on the sapphire substrate 12.

[0221] The buffer layer 14 may be made of n-type GaN, for example. Then-type contact layer 16 has a high n-type carrier concentration toensure ohmic contact smith the n-side electrode 34, and its material maybe GaN, for example. The n-type cladding layer 18 and the p-typecladding layer 22 function to confine carriers within the light emittinglayer 20. The light emitting layer 20 is a layer in which emissionoccurs due to recombination of electric charges injected as a currentinto the light emitting element.

[0222] The light emitting layer 20 may be made of undoped InGaN, forexample, and the cladding layers 18 and 22 may be made of AlGaN having alarger band gap than the light emitting layer 20. The p-type contactlayer 24 has a high p-type carrier concentration to ensure ohmic contactfifth the p-side electrode 26, and its material may be GaN, for example.

[0223] Stacked on the p-type contact layer 24 is the p-side electrode 26which is transparent to the emitted light. Stacked on the n-type contactlayer 18 is the n-side electrode 34. Bonding pads 32 of Au are stackedon these electrodes, respectively, so that N-wires (not shown) forsupplying a operating current to the element be bonded. The surface ofthe element is covered by the protective films 30 and 45 of siliconoxide, for example.

[0224] According to the embodiment, the fluorescent material is mixed inor deposited on either part of the element 10. Appropriate fluorescentmaterials being efficiently excited by a light in the ultraviolet bandare, for example, Y₂O₂S:Eu or La₂O₂S:(Eu,Sm) for mission of red light,(Sr, Ca, Ba, Eu)₁₀(PO₁)₆·Cl₂ for emission of blue light, and 3(Ba, Mg,Eu, Mn)O·8Al₂O₆ for emission of green light. By mixing these fluorescentmaterials in the appropriate ratio, almost all colors in the visiblewavelength range can be realized.

[0225] Most of these fluorescent materials have their absorption peaksin the wavelength band of about 300 to 380 nm. Therefore, in order toensure efficient wavelength conversion by the fluorescent materials, thelight emitting element 20 is preferably configured to emit ultravioletrays in the wavelength band below 380 nm. For maximizing the conversionefficiency by the fluorescent materials, the light emitting element ismore preferably configured to emit ultraviolet rays of a wavelength near330 nm.

[0226] The fluorescent material may be mixed in the p-side electrode 26.It also may be mixed in at least either of the protective films 30 and45. It also may be mixed in at least either of the semiconductor layers14 through 24 or substrate 12.

[0227] In order to mix the fluorescent material into the p-sideelectrode 26, a sputter deposition or a vacuum deposition, for example,can be used. When the p-side electrode 26 is formed by these method, thefluorescent material may be added. As for the protective films 30 and45, the same method may be used to incorporate the fluorescent material.A chemical vapor deposition i (CVD) may be also usable to incorporatethe fluorescent material.

[0228] The fluorescent material may be incorporated into the any one ofthe semiconductor layers 14 through 24 during the crystal growthprocess. It may also be incorporated into the semiconductor layer byusing the ion implantation after growing the layers. The ionimplantation is also usable to incorporate the fluorescent material intothe substrate 12.

[0229] The fluorescent material may also be deposited either on thesurface of the element 10 or between the any adjacent layers thereof.That is, it may be deposited between any adjacent layers of substrate 12through p-type contact layer 24, between the semiconductor layer and theprotective film 30, between the semiconductor layer and the electrode 26or 34, on the surface of the film 45, or on the surface of the electrode26 or 34. As the deposition method of the fluorescent material, forexample, electron beam vacuum deposition, sputtering deposition, andcoating method may be employed. The fluorescent material may be formedon the p-type contact layer 24 as a insulating layer, which functions asa current blocking layer.

[0230] In order to deposit the fluorescent material onto the surface ofthe light emitting element, one can disperse the fluorescent materialinto the appropriate solvent, coat it onto the light emitting elementand harden it up. As the solvent to disperse the fluorescent material,for example, alkalic silicate solution, silicate colloid aqua-solution,phosphate aqua-solution, organic solvent containing silicate compound,organic solvent containing rubber and natural glue aqua-solution may beused. Instead of dispersing the fluorescent material into these solventand coating it on the light emitting element, one can coat these solventwithout dispersing the fluorescent material then scatter or spray thefluorescent material on the coated solvent layer to deposit it, forexample.

[0231] According to the invention, by incorporating or depositing thefluorescent material on any part of the light emitting element, thelight emitted from the light emitting layer is efficiently convertedinto the secondary light having a longer wavelength.

[0232] For example, in the case that the light emitting layer 20 of theelement is made of GaN, the emitted primary light is a ultraviolet rayhaving a wavelength of 360 to 380 nanometers. The ultraviolet ray isconverted by the fluorescent material into a visible or infrared lighthaving a desired wavelength and the secondary light is extracted.

[0233] In the case that the light emitting layer 20 is made of InGaN, ablue light can be obtained depending on the mole fraction of indium (In)thereof. In that case, the fluorescent material which absorbs the bluelight and converts it into a light having a longer wavelength can beemployed. As such a fluorescent material, for example, organicfluorescent may be used in addition to the inorganic fluorescentexplained above. As such a organic fluorescent, rhodamine B for emissionof red light, brilliant sulfoflavine FF for emission of green light maybe used.

[0234] According to the embodiment, instead of extracting the primarylight from the light emitting layer, the primary light is converted bythe fluorescent material. Therefore, the fluctuation of the emissionwavelength caused by the change in process parameters, operating currentor temperature is dispelled. That is, according to the invention, theemission power and the emission wavelength can be independentlycontrolled.

[0235] Besides, according to the invention, by mixing the fluorescentmaterials aforementioned, a multi-wavelength emission is easilyrealized. For example, by mixing the fluorescent materials, emitting red(R), green (G) and blue (B) respectively, in an appropriate ratio, andby incorporating them into the light emitting element, a white light isreadily realized.

[0236] In FIG. 1, the gallium nitride compound semiconductor lightemitting element formed on the sapphire substrate is exemplary shown.However, the invention is not limited to the specific example, andapplicable to the any gallium nitride semiconductor light emittingelements formed on the substrate made of SiC, GaN, spinel, ZnO, Si orGaAs, for example.

[0237] As for the structure of the light emitting element, the inventionis not limited to the exemplary double-heterostructure and applicable tovarious structures such as the single heterostructure or multiquantumwell structure.

[0238] Explained next is a second light emitting element according tothe invention.

[0239]FIG. 2 is a cross-sectional view schematically shorting the secondsemiconductor light emitting element of the invention. The semiconductorlight emitting element 50 shown here is a zinc selenide (ZnSe)semiconductor light emitting element which has a multi-layered structureof semiconductors, namely, a buffer layer 54, n-type cladding layer 58,light emitting layer 60, p-type cladding layer 62 and transparentconductive layer 64 which are stacked in this order on a GaAs substrate52.

[0240] The buffer layer 54 may be made of n-type ZnSe, for example. Then-type cladding layer 58 and the p-type cladding layer 62 function toconfine carriers within the light emitting layer 60. These claddinglayers may be made of ZnSe having a larger band gap than the lightemitting layer 60. The light emitting layer 60 is a layer in whichemission occurs due to recombination of electric charges injected as acurrent into the light emitting element. The light emitting layer 60 maybe made of undoped ZnSe, for example. The transparent conductive layer64 is a electrically conductive layer having a high opticaltransparency, which may be made of indium tin oxide, for example.

[0241] Stacked on the conductive layer 64 is the p-side electrode 66which may be made of a metal such as gold (Au). On the bottom surface ofthe substrate 52, the n-side electrode 68 is formed. The surface of theelement is covered by the protective films 70 made of silicon oxide, forexample.

[0242] The ZnSe light emitting element 50 emits the light having awavelength of blue or blue-violet from its light emitting layer 60. Thisblue emission is converted by the fluorescent material into a visible orinfrared light having a longer wavelength which is extracted outside.

[0243] The fluorescent material can be incorporated into various part ofthe element 50 as explained with reference to the element 10. Forexample, it is incorporated into the p-side electrode 66, thetransparent conductive layer 64, any one of the semiconductor layers 54through 62 or substrate 52.

[0244] In order to mix the fluorescent material into the p-sideelectrode 66 or conductive layer 64, a sputter deposition or a vacuumdeposition, for example, can be used. When the conductive layer 64 orelectrode 66 is formed by these method, the fluorescent material may beadded. As for the protective film 70, the same method may be used toincorporate the fluorescent material. A chemical vapor deposition (CVD)may be also usable to incorporate the fluorescent material.

[0245] The fluorescent material may be incorporated into the any one ofthe semiconductor layers 54 through 62 during the crystal growthprocess. It may also be incorporated into the semiconductor layer byusing the ion implantation after growing the layers. The ionimplantation is also usable to incorporate the fluorescent material intothe substrate 52.

[0246] The fluorescent material may also be deposited either on thesurface of the element 50 or between the any adjacent layers thereof.That is, it may be deposited between any adjacent layers of substrate 52through conductive layer 64, between the semiconductor layer and theprotective film 70, between the semiconductor layer and the electrode 66or 68, on the surface of the film 70, or on the surface of the electrode66 or 68. As the deposition method of the fluorescent material, forexample, electron beam vacuum deposition, sputtering deposition, andcoating method may be employed. The fluorescent material may be formedon the conductive layer 64 as a insulating layer, which functions as acurrent blocking layer.

[0247] Although the ZnSe light emitting element is exemplary shown inFIG. 2, the invention is not limited to the specific example. Theinvention is also applicable to any other light emitting element made ofSiC, ZnS or BN, for example. These light emitting elements are capableof emitting a short wavelength emission such as blue with a highefficiency. The short wavelength emission is converted into the visibleor infrared light by the fluorescent material and extracted.

[0248] Next explained are 13 examples of the light emitting devicesmounted with the semiconductor light emitting element explained withreference to FIGS. 1 and 2.

[0249]FIG. 3 is a roughly illustrated cross-sectional view of a lightemitting device according to the invention. The light emitting device100A shown here is a device called “LED (light emitting diode) lamp” ofa so-called “lead frame type”. The device 100A includes a semiconductorlight emitting element 10 or 50 mounted on the bottom of a cup of a leadframe 110. The p-side electrode and the n-side electrode of the lightemitting element are connected to lead frames 110 and 120 by wires 130,130, respectively. Inner lead parts of the lead frames are protected bya resin 140.

[0250] According to the invention, the light emitting device 100A can beassembled by the same procedure as the conventional devices whichinclude no fluorescent material because the light emitting elementitself includes the fluorescent material. Besides, the durability ofdevice against the change in temperature is not degraded because theresin does not include the fluorescent material. Therefore, thereliability is improved as compared to the devices which includefluorescent material in their resin.

[0251] According to the invention, even if the emission from the lightemitting layer of the light emitting element is a ultraviolet ray whosewavelength is shorter than 380 nanometers, the resin or other part ofthe device is not damaged by the ultraviolet emission because theemission is converted into the longer wavelength light before it goesout from the light emitting element. The above mentioned advantagesabout the productivity and the reliability are good as well if asemiconductor laser is employed as the light emitting element. Also thedevice is easy to assemble because the cup enclosure to fill the resincontaining the fluorescent material is not necessary.

[0252]FIG. 4 is a roughly illustrated cross-sectional view of a lightemitting device according to the invention. The light emitting device200A shown here is a device called “LED (light emitting diode) lamp”of-a so-called “stem type”. The stem 210 includes the lead pins 222 and226 which are partially molded in the insulator 220. As the material ofthe insulator 220, ceramics or resin can be used. The lead pins 222 and226 have the outer lead part 224 and 228 extending to the outside. Theelement 10 or 50 is mounted onto the top of the lead pin 222 and theresin 240 is molded to protect the element. The one electrode of thelight emitting element is connected to the pin 226 by a wire 230.

[0253] By mounting with the light emitting element 10 or 50, the LEDlamp of the stem type as shown in Pig. 4 also has various advantages asexplained with reference to FIG. 3.

[0254]FIG. 5 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the invention. Thelight emitting device 250A shown here is a device called “SMD (surfacemounted device) lamp” of a so-called “substrate type”. The SMD lamp 250Ahas a substrate 260 which has electrode patterns 272 and 274. On one ofthe electrode patterns, the light emitting element 10 or 50 is mounted.As the material of the substrate, a resin such as epoxy, or ceramicssuch as alumina or glass may be employed. The electrode of the lightemitting element is connected to the pattern 274 by a wire 280. Thelight emitting element is protected by the resin 290.

[0255] By mounting with the light emitting element 10 or 50, the LEDlamp of the stem type as shown in FIG. 5 also has various advantages asexplained with reference to FIG. 3.

[0256]FIG. 6 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the invention. Thelight emitting device 300A shown here is a device called “SMD (surfacemounted device) lamp” of a so-called “lead frame type”. The SMD lamp300A has a lead frame 310 on which the light emitting element 10 or 50is mounted. As the material of the lead frame 310, a metal such ioncoated by tin is employed. The electrode of the light emitting elementis connected to the lead pin of the lead frame 310. The light emittingelement is protected by the resin 340.

[0257] By mounting with the light emitting element 10 or 50, the LEDlamp of the lead frame tripe as show-n in FIG. 6 also has variousadvantages as explained with reference to FIG. 3.

[0258]FIG. 7 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the invention. Thelight emitting device 350A shown here is a device called “planeremission type”. The planer emission type device 350A has lead frames 360and 362 on which the light emitting elements 10 or 50 are mountedrespectively. Each element is electrically connected to the lead framesby wire 380. The light emitting elements in the cup part of thereflector 370 are protected by the resin 390. The emission from eachelement is reflected by the reflector 370 and form a planer light whichis extracted.

[0259] By mounting with the light emitting element 10 or 50, the lightemitting device of the planer emission type as shown in FIG. 7 also hasvarious advantages as explained with reference to FIG. 3.

[0260]FIG. 8 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the invention. Thelight emitting device 400A shown here is a device called “dome type”.The dome type device 400A has a lead frame 410 on which a plurality(five to ten, for example) of the light emitting elements 10 or 50 aremounted peripherally. Each element is electrically connected to thecorresponding terminal pin of the lead frame 410 by wire (not shown).The light emitting elements are protected by the resin 440. The dometype light emitting device 400A can emit highly luminous and uniformlight because it has a many light emitting elements.

[0261] By mounting with the light emitting element 10 or 20, the lightemitting device of the dome type 400A as shown in FIG. 8 also hasvarious advantages as explained with reference to FIG. 3.

[0262]FIG. 9A is a roughly illustrated plan view and FIG. 9B is aroughly illustrated cross-sectional view of a seventh example of thelight emitting device according to the invention. The light emittingdevice 450A shown here is a device called “meter needle type”. Thedevice of this type is used for a self-illuminating needle of a metersuch as a speed meter of a vehicle. The light emitting device 450A has asubstrate or a lead frame 460 on which a plurality (five to twenty, forexample) of the light emitting elements 10 or 0 are mounted at certainintervals. Each element is electrically connected to the correspondingterminal pin by a wire (not shown). The light emitting elements areprotected by the resin 490. The meter needle type device 450A is mountedto a flange 466 and fixed to the axis of a speed meter, for example.

[0263] The meter needle type device 450A is compact and light-weight,and is capable of emitting a highly luminous and uniform light becauseit includes many light emitting elements.

[0264] By mounting with the light emitting elements 10 or 50, the lightemitting device of the meter needle type 450A as shown in FIG. 9 alsohas various advantages as explained with reference to FIG. 3.

[0265] Besides, emission color can be easily changed along the needle byarranging light emitting elements having a different emission color.According to the invention, it is easily realized only by changing thefluorescent material which is incorporated into the light emittingelement. The other materials and the basic structure of the lightemitting elements are the same each other. Therefore, the operatingcurrent and the voltage can be advantageously the same for all the lightemitting elements.

[0266]FIGS. 10A through 10D are roughly illustrated views of the eighthexample of the light emitting devices according to the invention. Thelight emitting devices 500A shown here are devices called “seven segmenttype” among which so-called “substrate type” is specifically shown inthe figure. The light emitting device of this type is used to indicate acharacter such as a digit or an alphabet. FIG. 10A is a perspective viewand FIG. 10B is a partially enlarged perspective view in a partiallysee-through mode. The substrate type includes a cavity type as shown inFIG. 10C as the cross sectional view and a resin mold type as shown inFIG. 10D as the cross sectional view. The light emitting element 10 or30 is electrically connected to the corresponding terminal pin by aAfire 530. The light emitted from the element is reflected by thereflector 520 and extracted. At the aperture, a color filter 544 and/ora diffusing film 548 is arranged.

[0267] By mounting with the a light emitting element 10 or 50, the lightemitting devices of the seven segment type 500A as shown in FIGS. 10Athrough 10D also have various advantages as explained with reference toFIG. 3.

[0268]FIG. 11 is a roughly illustrated cross sectional view of the ninthexample of the light emitting device according to the invention. Thelight emitting device 550A shown here is also a device called “sevensegment type” among which so-called “lead frame type” is specificallyshown in the figure. The light emitting element 10 or 50 according tothe invention is mounted on the lead frame 360 and is electricallyconnected to the corresponding terminal by a wire 580. The lightemitting element is molded by the resin 590. The light emitted from theelement is reflected by the reflector 570 and extracted.

[0269] By mounting Myth the a light emitting element 10 or 50, the lightemitting device of the seven segment type 50A as shown in FIG. 11 alsohas various advantages as explained with reference to FIG. 3.

[0270]FIG. 12A is a roughly illustrated plan view and FIG. 12B is aroughly illustrated cross-sectional view of a tenth example of the lightemitting device according to the invention. The light emitting device600A shown here is a device called “level meter type”. The device ofthis type is used as the level meter to indicate speed of a vehicle orrotation of an engine, for example. The level meter type device 600A hasa flange 602, and a substrate or a lead frame 610 on which a plurality(ten to thirty, for example) of the light emitting elements 10 or 50 aremounted at certain intervals. In many case, the elements are selectedand mounted so that the emission color changes continuously or step wisealong the line. Each element is connected to the corresponding terminalpin by a sire (not shown). The light emitting elements are protected bythe resin 640.

[0271] By mounting with the light emitting elements 10 or 50, the lightemitting device of the level meter type 600A as shown in FIGS. 12A and12B also have various advantages as explained with reference to FIG. 3.

[0272] In many case, such a light emitting device of the level metertype need to have light emitting elements having different emissioncolor. According to the invention, the emission color of each elementcan be easily changed only by changing the fluorescent material which isincorporated into the light emitting element. The other materials andthe basic structure of the light emitting elements remain the same eachother. Therefore, the operating current and the voltage can beadvantageously the same for all the light emitting elements.

[0273]FIG. 13A is a roughly illustrated perspective view and Fit. 13B isa roughly illustrated cross-sectional view of a eleventh example of thelight emitting device according to the invention. The light emittingdevice 650A shown here is a device called “matrix type”. The device ofthis type has a plurality of emission spot 652 which is arranged in agrid pattern, and is used to indicate characters, symbols or figures.

[0274] As shown in FIG. 13B, the device 650A has a substrate 660 onwhich a plurality of the light emitting elements 10 or 50 are mounted atcertain intervals. Each element is connected to the correspondingterminal by a wire (not shown). The light emitting elements areprotected by the resin 690. The emission from the element is reflectedby the reflector 670 and extracted. A color filter 692 and/or diffusingfilm 694 may be arranged if necessary.

[0275] By mounting with the light emitting elements 10 or 50, the lightemitting device of the matrix type 650A as shown in FIGS. 13A and 13Balso have various advantages as explained with reference to FIG. 3.

[0276] If the device 650A needs to have more than two kinds of emissioncolors, the emission color of each emission spot 692 can be easilychanged only by changing the fluorescent material of the correspondingelement. The materials and the basic structure of the each lightemitting element remain the same each other. Therefore, the operatingcurrent and the voltage of the each light emitting element can remainadvantageously the same. Besides, the fluctuation of the emission coloris fairly small.

[0277]FIG. 14 is a roughly illustrated perspective view of a twelfthexample of the light emitting device according to the invention. Thelight emitting device 700A shown here is a device called “array type”which is used as a light source of a facsimile or a image scanner. Thedevice of this type has a rail-like reflector 722 which is fixed to thesubstrate 720. A plurality of light emitting elements 10 or 50 accordingto the invention are mounted on the reflector 722. Between each of theelements, a separator 724 is located. A rod lens 740 is arranged abovethe light emitting elements and converge the emission from the element.

[0278] By mounting with the light emitting elements 10 or 50, the lightemitting device of the array type 700A as shown in FIG. 14 also hasvarious advantages as explained With reference to FIG. 3. Besides, thefluctuation of the emission color is fairly small.

[0279] If the device 700A needs to have more than two kinds of emissioncolors, the emission color of each element can be easily changed only bychanging the fluorescent material thereof. The materials and the basicstructure of the each light emitting element remain the same each other.Therefore, the operating current, the voltage and the size of the eachlight emitting element can remain advantageously the same.

[0280]FIG. 15 is a roughly illustrated cross sectional view of athirteenth example of the light emitting device according to theinvention. The light emitting device 750A shown here is a semiconductorlaser device called “can type”. The device of this type has a stem 770on which a semiconductor laser elements 10 or 50 according to theinvention is mounted. On the backside of the element, a photodetector775 is arranged to monitor the output of the element 10 or 50. The headof the stem 770 is sealed by the can 790. The laser beam emitted fromthe element is extracted through the window.

[0281] By mounting with the light emitting elements 10 or 50, the lightemitting device of the can type 750A as shown in FIG. 15 also hasvarious advantages as explained with reference to FIG. 3.

[0282] Next explained is a third embodiment of the invention.

[0283]FIG. 16 is a roughly illustrated cross sectional view of a exampleof the light emitting device according to the embodiment. The lightemitting device 100B shown here is a LED lamp of the lead frame type.According to the embodiment, the semiconductor light emitting element990 is mounted on the lead frame 110 then the fluorescent material isdeposited on the surface of the element 990 to from the fluorescentlayer FL.

[0284] In the embodiment, the element 990 need not to include afluorescent material. However, the element preferably have a luminousemission in the wavelength range of blue or ultraviolet in order toobtain a high conversion yield by using the fluorescent materials whichare easily available. As such a element having a light emitting layermade of, for example, gallium nitride, zinc selenide, silicon carbide orboron nitride may be employed.

[0285] In order to deposit the fluorescent material, first, thefluorescent material is dispersed into an appropriate solvent, then, itis coated on the surface of the element 990 and finally it is dried up.Another way to form the fluorescent layer is, first, coat an appropriatesolvent on the surface of the element 990, then, scatter or spray thefluorescent material onto the solvent, finally, harden it up.

[0286] The solvent is preferably adhesive. The examples of the solventare the ones including an inorganic polymer as a main component. Theones including a rubber material, farinaceous material or protein as amain component are also usable as the solvent. If the inorganic solventis used, the product advantageously becomes highly durable against theheat and chemicals and becomes flame-retardant. If the rubber material,the farinaceous material or the protein is used, the residual stress ofthe dried product is relaxed. Therefore, the problems caused by thestress such as deterioration of the device or the breakage of the wireare advantageously prevented. The farinaceous material and the proteinare also easy to handle because they are water-soluble.

[0287] The specific examples of the solvent are the alkalic silicatesolution, the silicate colloid aqua-solution, the phosphateaqua-solution, the organic solvent containing silicate compound, theorganic solvent containing rubber and the natural glue aqua-solution.

[0288] The refractive index of the dried product of the solvent may bepreferably between the refractive index of the surface of light emittingelement and the refractive index of its outside. For example, if thelight emitting element is molded by a resin, the refractive index of thedried product of the solvent preferably between the surface of lightemitting element and the refractive index of the resin. Thisrelationship in the refractive indices prevents the total reflection atthe emission edge of the element so that the external quantum efficiencyis improved.

[0289] As the fluorescent material of the embodiment, the inorganicmaterials or organic materials explained with reference to the firstembodiment may be used as well. The material should be selected so thata high conversion efficiency is obtained for the given wavelength ofsemiconductor element and the desired wavelength of the secondary light.

[0290] According to the embodiment, the fluorescent material FL isdeposited at the emission surface of the light emitting element 990.Therefore, almost 100% of the primary light emitted from the element isabsorbed and successfully converted by the fluorescent material. Theembodiment is especially advantageous, if the emission wavelength is theultraviolet having a wavelength shorter than 380 nanometers.

[0291] Besides, according to the embodiment, the light source is limitedto the vicinity of the emission edge of the light emitting element.Therefore, the optical path of the primary light in the fluorescentlayer FL becomes uniform and independent to the direction. This solvesthe problem that the wavelength of the secondary light varies dependingto the direction of the light.

[0292] Further, according to the embodiment, the secondary light can beeasily converged by using lenses or reflector, because the light sourceis limited to the vicinity of the emission edge of the light emittingelement. Therefore, the light emitting device having a high emissiondensity is realized. The inorganic polymer, the rubber material, thefarinaceous material or the protein have large volume contraction ratioswhen they dries up. Therefore, if any of these materials is used as amain component of a solvent to disperse the fluorescent material, thefluorescent material can be easily limited to the vicinity of theemission edge of the light emitting element. This makes theabove-mentioned advantages successfully realized.

[0293] Further according to the invention, by selecting the solvent sothat the refractive index thereof is between the refractive index of thelight emitting element and the refractive index of its adjacent layer,external quantum efficiency is further improved and high power lightemitting device is realized.

[0294] Next explained are specific examples of the embodiment. In theexplanation of these examples, the same components as those of the lightemitting device shown in FIGS. 1 through 16 are labeled with commonreference numerals, and their detailed explanation is omitted. FIG. 17is a roughly illustrated cross-sectional view of a light emitting deviceaccording to the invention. The light emitting device 200B shown here isa LED lamp of a stem type. The element 990 is mounted onto the top ofthe lead pin 222. The fluorescent layer FL is formed by any method asexplained above. In order to deposit the fluorescent layer FL, thefluorescent material may be dispersed in the solvent before it is coatedon the surface of the element or it may be sprayed after the solvent iscoated on the element.

[0295]FIG. 18 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the invention. Thelight emitting device 250B shown here is an SMD lamp of a substratetype. The light emitting element 10 or 50 is mounted on the substrate260 and the fluorescent layer FL is formed on it by any method asexplained above.

[0296]FIG. 19 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the invention. Thelight emitting device 300B shown here is an SMD lamp of a lead frametype. The light emitting element 990 is mounted on the lead frame 310,on which the fluorescent layer FL is formed by any method as explainedabove.

[0297]FIG. 20 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the invention. Thelight emitting device 350B shown here is a device of planer emissiontype. The light emitting elements 990 are mounted on the lead frames 360and 362 respectively, on which the fluorescent lasers FL is formed byany method as explained above.

[0298]FIG. 21 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the invention. Thelight emitting device 400B shown here is a device of the dome type. Thelight emitting elements 990 are mounted on the lead frame, on which thefluorescent layers FL is formed by any method as explained above.

[0299]FIG. 22A is a roughly illustrated plan view and FIG. 22B is aroughly illustrated cross-sectional view of a seventh example of thelight emitting device according to the invention. The light .emittingdevice 450 shown here is a device of a meter needle type. The lightemitting elements 990 are mounted in the lead frame 460, on which thefluorescent layers FL is formed by any method as explained above.

[0300]FIGS. 23A and 23B are roughly illustrated cross sectional views ofthe eighth example of the light emitting devices according to theinvention. The light emitting devices 5005 shown here are devices ofseven segment type of a substrate type. The cavity type is shown in FIG.23A and the resin mold type is shown in FIG. 23B.

[0301] The light emitting element 990 is mounted on the substrate 510,on which the fluorescent layers FL is formed by any method as explainedabove.

[0302]FIG. 24 is a roughly illustrated cross sectional view of the ninthexample of the light emitting device according to the invention. Thelight emitting device 550B shown here is also a device of seven segmenttype among, which the lead frame type is specifically shown in thefigure. The light emitting element 990 is mounted on the lead frame 560,on which the fluorescent layers FL is formed by any method as explainedabove.

[0303]FIG. 25 is a roughly illustrated cross-sectional view of a tenthexample of the light emitting device according to the invention. Thelight emitting device 650B shown here is a device of the matrix type. Aplurality of the light emitting elements 990 are mounted on thesubstrate 660, on which the fluorescent layers FL is formed by anymethod as explained above.

[0304]FIG. 26 is a roughly illustrated cross sectional view of aeleventh example of the light emitting device according to theinvention. The light emitting device 750B shown here is a semiconductorlaser device of the can type. The light emitting element 990, which is alaser diode in this specific case, is mounted on the stem 770, on whichthe fluorescent layers FL is formed by any method as explained above.

[0305] The above explained specific examples shown in FIG. 17 through 26also have various advantages as explained with reference to FIG. 16.

[0306] Next explained is a forth embodiment of the invention. In thefollowing explanations, the same components as those of the lightemitting device shown in FIGS. 1 through 26 are labeled with commonreference numerals, and their detailed explanation is omitted.

[0307]FIGS. 27A through 27C are a roughly illustrated cross sectionalview of a example of the light emitting device according to theembodiment. The light emitting devices 250C shown here are SMD lamps ofthe substrate type. In the example shown in FIG. 27A, a fluorescentmaterial is uniformly incorporated into resin 290.

[0308] In the example shown in FIG. 27B, a fluorescent material isincorporated with a high concentration at the surface region 290A of theresin 290. By precipitating the dispersed fluorescent material beforethe resin 290 is cured while keeping the device upside down, the highconcentration layer 290A of the fluorescent material is formed near thesurface of the resin 290. By adjusting the degree of the precipitation,the distribution of the fluorescent material can be controlled. If thefluorescent material is completely precipitated, thin fluorescent layeris formed on the surface of the resin 290, which is substantially thesame as coating the fluorescent material on the surface of the resin290.

[0309] In the example shown in FIG. 27C, a layer 290B including thefluorescent material is coated uniformly on the surface of the resin290. By coating a resin including the fluorescent material after theresin 290 is molded and cured, the uniform layer 290B including thefluorescent material can be formed. Alternatively, by molding the secondresin including the fluorescent material on the surface of the firstresin 290 after the resin 290 is molded and cured, the uniform layer290B including the fluorescent material can also be formed.

[0310] In the present embodiment, the element 990 need not to include afluorescent material. However, the element preferably have a luminousemission in the wavelength range of blue or ultraviolet in order toobtain a high conversion yield by using the fluorescent materials whichare easily available. As such a element having a light emitting layermade of, for example, gallium nitride, zinc selenide, silicon carbide orboron nitride may be employed.

[0311] As the fluorescent material of the embodiment, the inorganicmaterials or organic materials explained with reference to the firstembodiment may be used as well. The material should be selected so thata high conversion efficiency is obtained for the given wavelength ofsemiconductor element and the desired wavelength of the secondary light.

[0312] According to the embodiment, the fluorescent material isincorporated in the resin by the unique technique. Therefore, it is easyto get a multi-color emission, to prevent the fluctuation of theemission wavelength and to prevent the change in the emission wavelengthcaused by the increase in temperature. The embodiment is especiallyadvantageous, if the emission wavelength is the ultraviolet having awavelength shorter than 380 nanometers.

[0313] The SMD lamp of the embodiment is very compact and easy to mount,and can emit a white light. The conventional SMD lamp need to include alight scattering material in its resin to improve the uniformity of theemission. However, the light scattering material cause the decrease inintensity of the light output because it absorbs the emission. Incontrast to this, the SMD lamp of the embodiment emits a uniformluminous light because the incorporated fluorescent material alsofunctions as the light scattering material.

[0314] The SMD lamp shown in FIG. 27B and 27C can convert the primaryemission uniformly with a high efficiency because the fluorescentmaterial is located densely at the surface of the resin.

[0315] Next explained are specific examples of the embodiment. In theexplanation of these examples, the same components as those of the lightemitting device shown in FIGS. 1 through 27C are labeled with commonreference numerals, and their detailed explanation is omitted.

[0316]FIGS. 28A through 28C are roughly illustrated cross-sectionalviews of a second examples of the light emitting device according to theembodiment. The light emitting devices 300C shown here are SMD lamps ofa lead frame type.

[0317] In the example shown in FIG. 28A, a fluorescent material isuniformly incorporated into resin 340.

[0318] In the example shown in FIG. 28B, a fluorescent material isincorporated with a high concentration at the surface region 340A of theresin 340. By precipitating the dispersed fluorescent material beforethe resin 340 is cured while keeping the device upside down, the highconcentration layer 340A of the fluorescent material is formed near thesurface of the resin 340.

[0319] In the example shown in FIG. 28C, a layer 340B including thefluorescent material is coated uniformly on the surface of the resin340. By coating the second resin including the fluorescent materialafter the first resin 340 is molded and cured, the uniform layer 340Bincluding the fluorescent material can be formed. Alternatively, bymolding the second resin including the fluorescent material on thesurface of first resin 340 after the resin is molded and cured, theuniform layer 340B including the fluorescent material can also beformed.

[0320]FIGS. 29A through 29C are roughly illustrated cross-sectionalviews of third examples of the light emitting device according to theembodiment. The light emitting device 350C shown here is a device of theplaner emission type.

[0321] In the example shown in FIG. 29A, a fluorescent material isuniformly incorporated into resin 390. In the example shown in FIG. 29B,a fluorescent material is incorporated with a high concentration at thesurface region 390A of the resin 390. In the example shown in FIG. 29C,a layer including the fluorescent material is formed uniformly on thesurface of the resin 390. The fluorescent material can be incorporatedby the same way as explained with reference to the FIGS. 27A through27C.

[0322] According to the embodiment, a luminous uniform white emission isavailable.

[0323]FIGS. 30A through 30C are roughly illustrated cross-sectionalviews of a forth examples of the light emitting device according to theembodiment. The light emitting devices 400C shown here are of the dometype.

[0324] In the example shown in FIG. 30A, a fluorescent material isuniformly incorporated into resin 440. In the example shown in FIG. 30B,a fluorescent material is incorporated with a high concentration at thesurface region 440A of the resin 440. In the example shown in FIG. 30C,a layer 440B including the fluorescent material is coated uniformly onthe surface of the resin 440. The fluorescent material can beincorporated as explained with reference to the FIGS. 27A through 27C.

[0325] According to the embodiment, a dome type device having a luminousuniform white emission is available.

[0326]FIGS. 31A through 31C are roughly illustrated cross-sectionalviews of fifth examples of the light emitting device according to theembodiment. The light emitting devices 450C shown here are devices ofthe meter needle type.

[0327] In the example shown in FIG. 31A, a fluorescent material isuniformly incorporated into resin 490. In the example shown in FIG. 31B,a fluorescent material is incorporated with a high concentration at thesurface region 490A of the resin 490. In the example shown in FIG. 31C,a layer 490B including the fluorescent material is coated uniformly onthe surface of the resin 490. The fluorescent material can beincorporated as explained with reference to the FIGS. 27A through 27C.

[0328] According to the embodiment, a meter needle type device having aluminous uniform white emission is available. Especially, if used on theblack meter panel, the meter needle according to the embodiment has amuch improved contrast compared to the conventional red or greenneedles, which makes the driving of the vehicles much safer.

[0329]FIGS. 32A through 32C are roughly illustrated cross-sectionalviews of the sixth examples of the light emitting devices according tothe embodiment. The light emitting devices 500C shown here are devicesof the seven segment of the substrate type.

[0330] In the example shown in FIG. 32A, a fluorescent material isuniformly incorporated into resin 540. In the example shown in FIG. 32B,a fluorescent material is incorporated with a high concentration at thesurface region 540A of the resin 540. In the example shown in FIG. 32C,a layer 540B including the fluorescent material is coated uniformly onthe surface of the resin 540. The fluorescent material can beincorporated as explained with reference to the FIGS. 27A through 27C.

[0331] According to the embodiment, a seven segment type device having aluminous uniform white emission is available.

[0332]FIGS. 33A through 33C are roughly illustrated cross-sectionalviews of the seventh examples of the light emitting device according tothe embodiment. The light emitting devices 550C shown here are alsodevices of seven segment type of lead frame type.

[0333] In the example shown in FIG. 33A, a fluorescent material isuniformly incorporated into resin 590. In the example shown in FIG. 33B,a fluorescent material is incorporated with a high concentration at thesurface region 590A of the resin 590. In the example shown in FIG. 33C,a layer 590B including the fluorescent material is coated uniformly onthe surface of the resin 590. The fluorescent material can beincorporated as explained with reference to the FIGS. 27A through 27C.

[0334] According to the embodiment, a seven segment type device having aluminous uniform white emission is available. Besides, the viewing anglebecomes much wider compared to the conventional device because theprimary emission is converted into the secondary light near the surfaceof the device.

[0335]FIGS. 34A through 34C are roughly illustrated cross-sectionalviews of eighth examples of the light emitting device according to theembodiment. The light emitting device 600C shown here is a device of thematrix type.

[0336] In the example shown in FIG. 34A, a fluorescent material isuniformly incorporated into resin 690. In the example shown in FIG. 34B,a fluorescent material is incorporated with a high concentration at thesurface region 690A of the resin 690. In the example shown in FIG. 34C,a layer 690B including the fluorescent material is coated uniformly onthe surface of the resin 690. The fluorescent material can beincorporated as explained with reference to the FIGS. 27A through 27C.

[0337] According to the embodiment, a dot matrix type device having aluminous uniform white emission is available. Besides, a full-colordisplay is easily realized simply by using light emitting elementshaving a ultraviolet emission and by arranging the appropriatefluorescent material at the appropriate pixel to convert the primaryultraviolet emission into red, green or blue light. When the lightemitting elements are densely integrated, the caloric amount increases.However, the wavelength of the secondary emission does not changebecause the conversion function of the fluorescent material is stable.Besides, the viewing angle becomes much liter compared to theconventional device because the primary emission is converted into thesecondary light near the surface of the device.

[0338] The above explained specific examples of the forth embodiment ofthe invention shown in FIGS. 28A through 34C also have variousadvantages as explained with reference to FIGS. 27A through 27C.

[0339] Next explained is a fifth embodiment of the invention.

[0340]FIG. 35 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment. The lightemitting device 100D shown here is a LED lamp of the lead frame type.The semiconductor light emitting element 990 is mounted on the leadframe 110 then molded by the resin 140D. According to the embodiment, acavity 142 is formed inside the resin 140D. The deposited layer FL ofthe fluorescent material is formed on the inner wall of the cavity 142.

[0341] In the embodiment, the element 990 need not to include afluorescent material. However, the element preferably have a luminousemission in the wavelength range of blue or ultraviolet in order toobtain a high conversion yield by using the fluorescent materials whichare easily available. As such a element having a light emitting layermade of, for example, gallium nitride, zinc selenide, silicon carbide orboron nitride may be employed.

[0342] As the fluorescent material of the embodiment, the inorganicmaterials or organic materials explained with reference to the firstembodiment may be used as well. The material should be selected so thata high conversion efficiency is obtained for the given wavelength ofsemiconductor element and the desired wavelength of the secondary light.Also the fluorescent material preferably should be excited by theultraviolet lights. Because if the fluorescent materials is excited bythe visible lights, a cross-talk may occur between the adjacent devices.That is, the fluorescent material of one device is unnecessarily excitedby the emission from another device.

[0343] According to the embodiment, the fluorescent material FL isuniformly deposited at the emission surface of the light emittingelement 990. Therefore, almost 100% of the primary light emitted fromthe element is absorbed and uniformly converted by the fluorescentmaterial. The embodiment is especially advantageous, if the emissionwavelength is the ultraviolet having a wavelength shorter than 380nanometers.

[0344] Besides, according to the embodiment, the light source is limitedto the vicinity of the emission point of the light emitting element.Therefore, the optical path of the primary light in the fluorescentlayer FL becomes uniform and independent to the direction. This solvesthe problem that the wavelength of the secondary light varies dependingto the direction of the light.

[0345] Further, according to the embodiment, the light source is limitedto the vicinity of the emission point of the light emitting element.Therefore, the secondary light is easily converged by the lens effect ofthe resin 140D, which realizes the luminous output. This is especiallyadvantageous for the application of traffic signals and the outdoordisplays. If the cavity 142 is made big, the spot size of the lightbecomes larger, which is advantageous for the indicators.

[0346] Next explained are specific examples of the embodiment. In theexplanation of these examples, the same components as those of the lightemitting device shown in FIGS. 1 through 35 are labeled With commonreference numerals, and their detailed explanation is omitted. FIG. 36is a roughly illustrated cross-sectional view of a light emitting deviceaccording to the embodiment. The light emitting device 200D shown hereis a LED lamp of a stem type. A cavity 242 is formed in the resin 240D.The deposited layer FL of the fluorescent material is formed on theinner wall of the cavity 242.

[0347]FIG. 37 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment. Thelight emitting device 250D shown here is an SMD lamp of a substratetype. A cavity 292 is formed in the resin 290D. The deposited layer FLof the fluorescent material is formed on the inner wall of the cavity292.

[0348]FIG. 38 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment. Thelight emitting device 350D shown here is a device of a planar emissiontype. A cavity 392 is formed in the resin 390D. The deposited layer FLof the fluorescent material is formed on the inner wall of the cavity392.

[0349]FIG. 39 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment. Thelight emitting device 400D shown here is a device of a dome type. Acavity 442 is formed in the resin 440D. The deposited layer FL of thefluorescent material is formed on the inner wall of the cavity 442.

[0350]FIG. 40 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment. Thelight emitting device 500D shown here is a device of a seven segmenttype of a substrate type. A cavity 542 is formed in the resin 540D. Thedeposited layer FL of the fluorescent material is formed on the innerwall of the cavity 542.

[0351] The above explained specific examples shown in FIGS. 36 through40 also have various advantages as explained with reference to FIG. 35.

[0352] Next explained is a sixth embodiment of the invention. In thefollowing explanations, the same components as those of the lightemitting device shown in FIGS. 1 through 40 are labeled with commonreference numerals, and their detailed explanation is omitted.

[0353]FIG. 41 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment. The lightemitting device 100E shown here is a LED lamp of the lead frame type.The semiconductor light emitting element 990 is mounted on the leadframe 110 then the resin 140E is molded. According to the embodiment, adipping resin 142E is formed inside the molded resin 140E. The resin142E contains the fluorescent material. The resin called hereafter“dipping resin” is a resin formed without using a mold. The “dippingresin” is formed by dripping the resin material from a dispenser ontothe element or by dipping the element in the resin material. The resinmaterial contains the resin in a appropriate solvent. According to theembodiment, the element 990 is first sealed by the dipping resin 142Ewhich contains the fluorescent material, then the molded resin 140E isformed.

[0354] In the embodiment, the element 990 need not to include afluorescent material. However, the element preferably have a luminousemission in the wavelength range of blue or ultraviolet in order toobtain a high conversion yield by using the fluorescent materials whichare easily available. As such a element having a light emitting layermade of, for example, gallium nitride, zinc selenide, silicon carbide orboron nitride may be employed.

[0355] As the fluorescent material of the embodiment, the inorganicmaterials or organic materials explained with reference to the firstembodiment may be used as well. The material should be selected so thata high conversion efficiency is obtained for the given wavelength ofsemiconductor element and the desired wavelength of the secondary light.Also the fluorescent material preferably should be excited by theultraviolet lights. Because if the fluorescent materials is excited bythe visible lights, a cross-talk may occur between the adjacent devices.That is, the fluorescent material of one device is unnecessarily excitedby the emission from another device.

[0356] According to the embodiment, the fluorescent material FL isuniformly located around the light emitting element 990. Therefore,almost 100% of the primary light emitted from the element is absorbedand uniformly converted by the fluorescent material. The embodiment isespecially advantageous, if the emission wavelength is the ultraviolethaving a wavelength shorter than 380 nanometers.

[0357] Also, the emission wavelength becomes fairly stabilized becausethe primary light from the element is converted into the secondarylight. The wavelength of the resultant secondary light is not affectedby the fluctuation of the wavelength of the primary emission.Accordingly, the wavelength of the secondary light is independent to theoperating current or voltage applied to the element.

[0358] Further, according to the embodiment, the light source is limitedto the vicinity of the emission point of the light emitting element.Therefore, the secondary light is easily converged by the lens effect ofthe resin 140E, which realizes the luminous output. This is especiallyadvantageous for the application of traffic signals and the outdoordisplays. If the dipping resin 142E is made big, the spot size of thelight becomes larger, which is advantageous for the indicators.

[0359] Next explained are specific examples of the embodiment. In theexplanation of these examples, the same components as those of the lightemitting device shown in FIGS. 1 through 41 are labeled with commonreference numerals, and their detailed explanation is omitted. FIG. 42is a roughly illustrated cross-sectional view, of a light emittingdevice according to the embodiment. The light emitting device 200E shownhere is a LED lamp of a stem type. A dipping resin 242E is formed in thedipped resin 240E. The dipping resin 242E contains the fluorescentmaterial.

[0360]FIG. 43 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment. Thelight emitting device 250E shown here is an SMD lamp of a substratetype. A dipping resin 292E is formed in the molded resin 290E. Thedipping resin 292E contains the fluorescent material.

[0361]FIG. 44 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment. Thelight emitting device 350E shown here is a device of a planar emissiontype. A dipping resin 392E is formed in the molded resin 390E. Thedipping resin 392E contains the fluorescent material.

[0362]FIG. 45 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment. Thelight emitting device 400E shown here is a device of a dome type. Adipping resin 442B is formed in the molded resin 440E. The dipping resin442E contains the fluorescent material.

[0363]FIG. 46 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment. Thelight emitting device 500E shown here is a device of a seven segmenttype of a substrate type. A dipping resin 542E is formed under themolded resin 540E. The dipping resin 542E contains the fluorescentmaterial.

[0364] The above explained specific examples shown in FIGS. 42 through46 also have various advantages as explained with reference to FIG. 41.

[0365] Next explained is a seventh embodiment of the invention.

[0366] In the following explanations, the same components as those ofthe light emitting device shown in FIGS. 1 through 46 are labeled withcommon reference numerals, and their detailed explanation is omitted.

[0367]FIG. 47 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment. The lightemitting device 100F shown here is a LED lamp of the lead frame type.The semiconductor light emitting element 990 is mounted on the leadframe 110 then the resin 140F is molded. According to the embodiment, adipping resin 142F is formed inside the molded resin 140F. The layer FLof the fluorescent material is formed on the surface of the dippingresin 142F. The element 990 is first sealed by the dipping resin 142F.Then the fluorescent material with an appropriate medium is coated onthe surface of the dipping resin 142F. Finally, the resin 140F ismolded.

[0368] In order to form the layer FL containing the fluorescentmaterial, first, the methods as explained with reference to FIG. 16 canbe used as well. That is, the fluorescent material is dispersed into anappropriate solvent, then, it is coated on the surface of the element990 and finally, it is dried up. Another way to form the fluorescentlayer is, first, coat an appropriate solvent on the surface of theelement 990, then, scatter or spray the fluorescent material onto thesolvent, finally, harden it up.

[0369] The solvent is preferably adhesive. The examples of the solventare the ones including an inorganic polymer as a main component. Theones including a rubber material, farinaceous material or protein as amain component are also usable as the solvent. If the inorganic solventis used, the product advantageously becomes highly durable against theheat and chemicals and becomes flame-retardant. If the rubber material,the farinaceous material or the protein is used, the residual stress ofthe dried product is relaxed. The farinaceous material and the proteinare also easy to handle because they are water-soluble. The specificexamples of the solvent are the alkalic silicate solution, the silicatecolloid aqua-solution, the phosphate aqua-solution, the organic solventcontaining silicate compound, the organic solvent containing rubber andthe natural glue aqua-solution.

[0370] In the embodiment, the element 990 need not to include afluorescent material. However, the element preferably have a luminousemission in the wavelength range of blue or ultraviolet in order toobtain a high conversion yield by using the fluorescent materials whichare easily available. As such a element having a light emitting layermade of, for example, gallium nitride, zinc selenide, silicon carbide orboron nitride may be employed.

[0371] As the fluorescent material of the embodiment, the inorganicmaterials or organic materials explained with reference to the firstembodiment may be used as well. The material should be selected so thata high conversion efficiency is obtained for the given wavelength ofsemiconductor element and the desired wavelength of the secondary light.Also the fluorescent material preferably should be excited by theultraviolet lights. Because if the fluorescent materials is excited bythe visible lights, a cross-talk may occur between the adjacent devices.That is, the fluorescent material of one device is unnecessarily excitedby the emission from another device.

[0372] According to the embodiment, the fluorescent material FL isuniformly located around the light emitting element 990. Therefore,almost 100% of the primary light emitted from the element is absorbedand uniformly converted by the fluorescent material. The embodiment isespecially advantageous, if the emission wavelength is the ultraviolethaving a wavelength shorter than 380 nanometers.

[0373] Also, the emission wavelength becomes fairly stabilized becausethe primary light from the element is converted into the secondarylight. The wavelength of the resultant secondary light is not affectedby the fluctuation of the wavelength of the primary emission.Accordingly, the wavelength of the secondary light is independent to theoperating current or voltage applied to the element.

[0374] Further, according to the embodiment, the light source is limitedto the vicinity of the emission point of the light emitting element.Therefore, the secondary light is easily converged by the lens effect ofthe resin 140F, which realizes the luminous output. This is especiallyadvantageous for the application of traffic signals and the outdoordisplays. If the dipping resin 142F is made big, the spot size of thelight becomes larger, which is advantageous for the indicators.

[0375] Next explained are specific examples of the embodiment. In theexplanation of these examples, the same components as those of the lightemitting device shown in FIGS. 1 through 47 are labeled with commonreference numerals, and their detailed explanation is omitted. FIG. 48is a roughly illustrated cross-sectional view of a light emitting deviceaccording to the embodiment. The light emitting device 200F shown hereis a LED lamp of a stem type. A dipping resin 242F is formed in thedipped resin 240F. The layer FL containing the fluorescent material isformed on the dipping resin 242F.

[0376]FIG. 49 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment. Thelight emitting device 250F shown here is an SMD lamp of a substratetype. A dipping resin 292F is formed in the molded resin 290F. The layerFL containing the fluorescent material is formed on the dipping resin292F.

[0377]FIG. 50 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment. Thelight emitting device 350F shown here is a device of a planar emissiontype. A dipping resins 392F are formed in the molded resin 390F. Thelayers FL containing the fluorescent material are formed on the dippingresins 392F.

[0378]FIG. 51 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment. Thelight emitting device 400F shown here is a device of a dome type. Adipping resin 442F is formed in the molded resin 440F. The layer FLcontaining the fluorescent material is formed on the dipping resin 442F.

[0379]FIG. 52 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment. Thelight emitting device 500F shown here is a device of a seven segmenttype of a substrate type. A dipping resin 542F is formed under themolded resin 540F. The layer FL containing the fluorescent material isformed on the dipping resin 542F.

[0380] The above explained specific examples shown in FIGS. 48 through52 also have various advantages as explained with reference to FIG. 47.

[0381] Next explained is a eighth embodiment of the invention. In thefollowing explanations, the same components as those of the lightemitting device shown in FIGS. 1 through 52 are labeled with commonreference numerals, and their detailed explanation is omitted.

[0382]FIG. 53 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment. The lightemitting device 100G shown here is a LED lamp of the lead frame type.The semiconductor light emitting element 990 is mounted on the leadframe 110G then the resin 140 is molded. According to the embodiment,the lead frame 110G and 120G contains the fluorescent material whichabsorbs the primary light emitted from the element 990 and emits thesecondary light.

[0383] In the embodiment, the element 990 also need not to include afluorescent material. However, the element preferably have a luminousemission in the wavelength range of blue or ultraviolet in order toobtain a high conversion yield by using the fluorescent materials whichare easily available. As such a element having a light emitting layermade of, for example, gallium nitride, zinc selenide, silicon carbide orboron nitride may be employed.

[0384] As the fluorescent material of the embodiment, the inorganicmaterials or organic materials explained lath reference to the firstembodiment may be used as well. The material should be selected so thata high conversion efficiency is obtained for the given wavelength ofsemiconductor element and the desired wavelength of the secondary light.Also the fluorescent material preferably should be excited by theultraviolet lights. Because if the fluorescent materials is excited bythe visible lights, a cross-talk may occur between the adjacent devices.That is, the fluorescent material of one device is unnecessarily excitedby the emission from another device.

[0385] According to the embodiment, the emission wavelength becomesfairly stabilized because the primary light from the element isconverted into the secondary light. The wavelength of the resultantsecondary light is not affected by the fluctuation of the wavelength ofthe primary emission. Accordingly, the wavelength of the secondary lightis independent to the operating current or voltage applied to theelement.

[0386] Next explained are specific examples of the embodiment. In theexplanation of these examples, the same components as those of the lightemitting device shown in FIGS. 1 through 53 are labeled with commonreference numerals, and their detailed explanation is omitted. FIG. 54is a roughly illustrated cross-sectional view of a light emitting deviceaccording to the embodiment. The light emitting device 200G shown hereis a LED lamp of a stem type. The fluorescent material is incorporatedin the insulative part 220G of the stem 210G.

[0387]FIG. 55 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment. Thelight emitting device 250G shown here is an SMD lamp of a substratetype. The fluorescent material is incorporated in the substrate 260G.

[0388]FIG. 56 s a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment. Thelight emitting device 300G shown here is an SMD lamp of a lead frametype. The fluorescent material is incorporated in the lead frame 310G.

[0389]FIG. 57 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment. Thelight emitting device 350G shown here is a device of a planar emissiontype. The fluorescent material is incorporated in the lead frame 360Gand 362G.

[0390]FIG. 58 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment. Thelight emitting device 400G shown here is a device of a dome type. Thefluorescent material is incorporated in the lead frame 410G.

[0391]FIGS. 59A and 59B are a roughly illustrated view and across-sectional view of a seventh example of the light emitting deviceaccording to the embodiment respectively. The light emitting device 450Gshown here is a device of a meter needle type. The fluorescent materialis incorporated in the substrate 460G.

[0392]FIG. 60 is a roughly illustrated cross-sectional view of a eighthexample of the light emitting device according to the embodiment. Thelight emitting device 500G shown here is a device of a seven segmenttype of a substrate type. The fluorescent material is incorporated inthe substrate 5010G. The embodiment is also applied to the device of aresin mold tape in addition to the illustrated cavity type in thefigure.

[0393]FIG. 61 is a roughly illustrated cross-sectional view of a ninthexample of the light emitting device according to the embodiment. Thelight emitting device 550G shown here is a device of a seven segmenttype of a lead frame type. The fluorescent material is incorporated inthe lead frame 560G.

[0394]FIG. 62 is a roughly illustrated cross-sectional view of a tenthexample of the light emitting device according to the embodiment. Thelight emitting device 650G shone here is a device of a matrix type. Thefluorescent material is incorporated in the substrate 660G. FIG. 63 is aroughly illustrated cross-sectional view of a eleventh example of thelight emitting device according to the embodiment. The light emittingdevice 700G shown here is a device of an array tape. The fluorescentmaterial is incorporated in the substrate 720G or the reflector 722G.

[0395]FIG. 64 is a roughly illustrated cross-sectional view of a twelfthexample of the light emitting device according to the embodiment. Thelight emitting device 750G shown here is a laser sol device of a cantype. The fluorescent material is incorporated in the stem 770G.

[0396] The above explained specific examples shown in FIGS. 54 through64 also have various advantages as explained with reference to FIG. 53.

[0397] Next explained is a ninth embodiment of the invention. Accordingto the embodiment, the fluorescent material is located under the lightemitting element. More specifically, the fluorescent material is placedat the mounting part of the lead frame, stem or substrate, on which theelement is mounted.

[0398] In the following explanations, the same components as those ofthe light emitting device shown in FIGS. 1 through 64 are labeled withcommon reference numerals, and their detailed explanation is omitted.

[0399]FIG. 65 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment. The lightemitting device 100H shown here is a LED lamp of the lead frame type.The semiconductor light emitting element 990 is mounted on the leadframe 110 then the resin 140 is molded. According to the embodiment, thelayer FL containing the fluorescent material is placed between the leadframe 110 and the light emitting element 990. The fluorescent materialin the layer FL absorbs the primary light emitted from the element 990and emits the secondary light.

[0400] The one method to form the layer FL is to incorporate thefluorescent material into the adhesive which is used to fix the element990 onto the lead frame. As such a adhesive, for example, resinmaterials, rubber materials, organic materials, inorganic materials,farinaceous materials, protein materials, tar materials or metal solderscan be used. If the inorganic material is used, the productadvantageously becomes highly durable against the heat and chemicals andbecomes flame-retardant. If any of the rubber materials, organicmaterials, the farinaceous materials or the protein materials is used,the residual stress of the dried product is relaxed. Therefore, theproblems caused by the stress such as deterioration of the device or thebreakage of the wire are advantageously prevented. The farinaceousmaterials and the protein materials are also easy to handle because theyare water-soluble.

[0401] According to the embodiment, the fluorescent material isdispersed in the adhesive and coated onto the lead frame to from thelayer FL.

[0402] The another method to form the layer FL is to coat thefluorescent material on the mounting surface of the lead frame first,then to mount the element 990 by using a adhesive. As the solvent todisperse the fluorescent materials, the one as explained with referenceto FIG. 16 can be used as well.

[0403] The third method to form the layer FL is to use a preformedtablet of the layer FL including the fluorescent material. That is, fixthe preform onto the mounting surface of the lead frame, then mount thelight emitting element 990 on the tablet.

[0404] In the embodiment, the element 990 also need not to include afluorescent material. However, the element preferably have a luminousemission in the wavelength range of blue or ultraviolet in order toobtain a high conversion yield by using the fluorescent materials whichare easily available. As such a element having a light emitting layermade of, for example, gallium nitride, zinc selenide, silicon carbide orboron nitride may be employed.

[0405] As the fluorescent material of the embodiment, the inorganicmaterials or organic materials explained with reference to the firstembodiment may be used as well. The material should be selected so thata high conversion efficiency is obtained for the given wavelength ofsemiconductor element and the desired wavelength of the secondary light.Also the fluorescent material preferably should be excited by theultraviolet lights. Because if the fluorescent materials is excited bythe visible lights, a cross-talk may occur between the adjacent devices.That is, the fluorescent material of one device is unnecessarily excitedby the emission from another device.

[0406] According to the embodiment, the emission wavelength becomesfairly stabilized because the primary light from the element isconverted into the secondary light. The wavelength of the resultantsecondary light is not affected by the fluctuation of the wavelength ofthe primary emission. Accordingly, the wavelength of the secondary lightis independent to the operating current or voltage applied to theelement.

[0407] Next explained are specific examples of the embodiment. In theexplanation of these examples, the same components as those of the lightemitting device shown in FIGS. 1 through 65 are labeled with commonreference numerals, and their detailed explanation is omitted. FIG. 66is a roughly illustrated cross-sectional view of a light emitting deviceaccording to the embodiment. The light emitting device 200H shown hereis a LED lamp of a stem type. The layer FL including the fluorescentmaterial is placed between the stem 210 and the light emitting element990 by one of any method as explained above.

[0408]FIG. 67 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment. Thelight emitting device 250H shown here is an SMD lamp of a substratetype. The layer FL including the fluorescent material is placed betweenthe substrate 260 and the light emitting element 990.

[0409]FIG. 68 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment. Thelight emitting device 300H shown here is an SMD lamp of a lead frametype. The layer FL including the fluorescent material is placed betweenthe lead frame 310 and the light emitting element 990.

[0410]FIG. 69 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment. Thelight emitting device 350H shown here is a device of a planar emissiontype. The layers FL including the fluorescent material are placedbetween the lead frames 360, 362 and the light emitting element 990.

[0411]FIG. 70 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment. Thelight emitting device 400H shown here is a device of a dome type. Thelayer FL including the fluorescent material is placed between the leadframes 410 and the light emitting element 990.

[0412]FIGS. 71A and 71B are a roughly illustrated plan view and across-sectional view of a seventh example of the light emitting deviceaccording to the embodiment respectively. The light emitting device 450Hshown here is a device of a meter needle type. The layer FL includingthe fluorescent material is placed between the substrate 460 and thelight emitting element 990.

[0413]FIG. 72 is a roughly illustrated cross-sectional view of a eighthexample of the light emitting device according to the embodiment. Thelight emitting device 500H shown here is a device of a seven segmenttype of a substrate type. The layer FL including the fluorescentmaterial is placed between the substrate 510 and the light emittingelement 990. The embodiment is also applied to the device of a resinmold type in addition to the cavity type illustrated in the figure.

[0414]FIG. 73 is a roughly illustrated cross-sectional view of a ninthexample of the light emitting device according to the embodiment. Thelight emitting device 950H shown here is a device of a seven segmenttype of a lead frame type. The layer FL including the fluorescentmaterial is placed between the lead frame 560 and the light emittingelement 990.

[0415]FIG. 74 is a roughly illustrated cross-sectional view of a tenthexample of the light emitting device according to the embodiment. Thelight emitting device 650H shown here is a device of a matrix tripe. Thelayer FL including the fluorescent material is placed between thesubstrate 660 and the light emitting element 990.

[0416]FIG. 75 is a roughly illustrated cross-sectional view of aeleventh example of the light emitting device according to theembodiment. The light emitting device 700H shown here is a device of anarray type. The layer FL including the fluorescent material is placedbetween the reflector 722 and the light emitting element 990.

[0417]FIG. 76 is a roughly illustrated cross-sectional view of a twelfthexample of the light emitting device according to the embodiment. Thelight emitting device 750H shown here is a laser device of a can type.The layer FL including the fluorescent material is placed between thestem 770 and the light emitting element 990.

[0418] The above explained specific examples shown in FIGS. 66 through76 also have various advantages as explained with reference to FIG. 65.

[0419] Next explained is a tenth embodiment of the invention. Accordingto the embodiment, the fluorescent material is coated onto thereflective surface, such as the upper surface of a lead frame, of thelight emitting device.

[0420] In the following explanations, the same components as those ofthe light emitting device shown in FIGS. 1 through 76 are labeled withcommon reference numerals, and their detailed explanation is omitted.

[0421]FIG. 77 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment. The lightemitting device 100I shown here is a LED lamp of the lead frame type.The semiconductor light emitting element 990 is mounted on the leadframe 110 then the resin 140 is molded. According to the embodiment, thelayer FL containing the fluorescent material is formed on the reflectivesurface of the lead frame 110, which absorbs the primary light emittedfrom the element 990 and emits the secondary light.

[0422] According to the embodiment, the fluorescent material isdispersed in an appropriate medium or solvent and coated onto the leadframe, then it is dried up. As such a medium or a solvent, for example,resin materials, rubber materials, organic materials, inorganicmaterials, farinaceous materials, protein materials, tar materials ormetal solders can be used. If the inorganic material is used, theproduct advantageously becomes highly durable against the heat andchemicals and becomes flame-retardant. If any of the rubber materials,organic materials, the farinaceous materials or the protein materials isused, the residual stress of the dried product is relaxed. Therefore,the problems caused by the stress such as deterioration of the device orthe breakage of the wire are advantageously prevented. The farinaceousmaterials and the protein materials are also easy to handle because theyare water-soluble.

[0423] In the embodiment, the element 990 also need not to include afluorescent material. However, the element preferably have a luminousemission in the wavelength range of blue or ultraviolet in order toobtain a high conversion yield by using the fluorescent materials whichare easily available. As such a element having a light emitting layermade of, for example, gallium nitride, zinc selenide, silicon carbide orboron nitride may be employed.

[0424] As the fluorescent material of the embodiment, the inorganicmaterials or organic materials explained Kith reference to the firstembodiment may be used as well. The material should be selected so thata high conversion efficiency is obtained for the given wavelength ofsemiconductor element and the desired wavelength of the secondary light.Also the fluorescent material preferably should be excited by theultraviolet lights. Because if the fluorescent materials is excited bythe visible lights, a cross-talk may occur between the adjacent devices.That is, the fluorescent material of one device is unnecessarily excitedby the emission from another device.

[0425] According to the embodiment, the emission wavelength becomesfairly stabilized because the primary light from the element isconverted into the secondary light. The wavelength of the resultantsecondary light is not affected by the fluctuation of the wavelength ofthe primary emission. Accordingly, the wavelength of the secondary lightis independent to the operating current or voltage applied to theelement.

[0426] Next explained are specific examples of the embodiment. In theexplanation of these examples, the same components as those of the lightemitting device shown in FIGS. 1 through 77 are labeled with commonreference numerals, and their detailed explanation is omitted. FIG. 78is a roughly illustrated cross-sectional view of a light emitting deviceaccording to the embodiment. The light emitting device 2001 shown hereis a LED lamp of a stem type. The layer FL including the fluorescentmaterial is formed on the reflective surface of the stem 210.

[0427]FIG. 79 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment. Thelight emitting device 250I shown here is an SMD lamp of a substratetype. The layer FL including the fluorescent material is formed on thereflective surface of the substrate 260.

[0428]FIG. 80 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment. Thelight emitting device 3001 shown here is an SMD lamp of a lead frametype. The layer FL including the fluorescent material is formed on thereflective surface of the lead frame 310.

[0429]FIG. 81 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment. Thelight emitting device 3501 shown here is a device of a planar emissiontype. The layer FL including the fluorescent material is formed on thereflector 370.

[0430]FIG. 82 is a roughly illustrated cross-sectional view of a sixthexample of the light emitting device according to the embodiment. Thelight emitting device 4001 shown here is a device of a dome type. Thelayer FL including the fluorescent material is formed in the reflectivesurface of the lead frame 410.

[0431]FIGS. 83A and 83B are a roughly illustrated plan view and across-sectional view of a seventh example of the light emitting deviceaccording to the embodiment respectively. The light emitting device 4501shown here is a device of a meter needle type. The layer FL includingthe fluorescent material is formed on the reflective surface of thesubstrate 460.

[0432]FIG. 84 is a roughly illustrated cross-sectional view of a eighthexample of the light emitting device according to the embodiment. Thelight emitting device 5001 shown here is a device of a seven segmenttype of a substrate type. The layer FL including the fluorescentmaterial is formed on the reflector 520. The embodiment is also appliedto the device of a resin mold type in addition to the cavity typeillustrated in the figure.

[0433]FIG. 85 is a roughly illustrated cross-sectional view of a ninthexample of the light emitting device according to the embodiment. Thelight emitting device 550I shown here is a device of a seven segmenttype of a lead frame type. The layer FL including the fluorescentmaterial is formed on the reflector 570.

[0434]FIG. 86 is a roughly illustrated cross-sectional view of a tenthexample of the light emitting device according to the embodiment. Thelight emitting device 6501 shown here is a device of a matrix type. Thelayer FL including the fluorescent material is placed on the reflector670.

[0435]FIG. 87 is a roughly illustrated cross-sectional view of aeleventh example of the light emitting device according to theembodiment. The light emitting device 7001 shown here is a device of anarray type. The layer FL including the fluorescent material is formed onthe reflector 722 and/or on the separator 724.

[0436]FIG. 88 is a roughly illustrated cross-sectional view of a twelfthexample of the light emitting device according to the embodiment. Thelight emitting device 750I shown here is a laser device of a can type.The layer FL including the fluorescent material is formed on thereflective surface of the stem 770.

[0437] The above explained specific examples shown in FIGS. 78 through88 also have various advantages as explained with reference to FIG. 77.

[0438] Next explained is a eleventh embodiment of the invention.According to the embodiment, the fluorescent material is located at thelight extraction part, such as the surface of the resin, the lens, orthe window, of the light emitting devices.

[0439] In the following explanations, the same components as those ofthe light emitting device shown in FIGS. 1 through 88 are labeled withcommon reference numerals, and their detailed explanation is omitted.

[0440]FIG. 89 is a roughly illustrated cross-sectional view of a exampleof the light emitting device according to the embodiment. The lightemitting device 300J shown here is a light emitting device of the planeremission type. The layer FL containing the fluorescent material isformed on the window, i.e. the resin 390, which absorbs the primarylight emitted from the element 990 and emits the secondary light.

[0441] In order to from the layer FL, the fluorescent material can alsobe dispersed in an appropriate medium or solvent and coated onto thelead frame, then dried up. As such a medium or a solvent, for example,resin materials, rubber materials, organic materials, inorganicmaterials, farinaceous materials, protein materials, tar materials ormetal solders can be used. If the inorganic material is used, theproduct advantageously becomes highly durable against the heat andchemicals and becomes flame-retardant. If any of the rubber materials,organic materials, the farinaceous materials or the protein materials isused, the residual stress of the dried product is relaxed. Therefore,the problems caused by the stress such as a crack of the layer areadvantageously prevented. The farinaceous materials and the proteinmaterials are also easy to handle because they are water-soluble.

[0442] Alternatively, a light transmissive film can be employed to formthe layer FL. The fluorescent material can be coated on the surface ofthe film or dispersed in the film.

[0443] In the case of the device having a lens, the fluorescent materialcan be coated on the surface of the lens of dispersed in the lens.

[0444] According to the embodiment, the light emitting element 990 alsoneed not to include a fluorescent material. However, the elementpreferably have a luminous emission in the wavelength range of blue orultraviolet in order to obtain a high conversion yield by using thefluorescent materials which are easily available. As such a elementhaving a light emitting layer made of, for example, gallium nitride,zinc selenide, silicon carbide or boron nitride may be employed.

[0445] As the fluorescent material of the embodiment, the inorganicmaterials or organic materials explained with reference to the firstembodiment may be used as well. The material should be selected so thata high conversion efficiency is obtained for the given wavelength ofsemiconductor element and the desired wavelength of the secondary light.Also the fluorescent material preferably should be excited by theultraviolet lights. Because if the fluorescent materials is excited bythe visible lights, a cross-talk may occur between the adjacent devices.That is, the fluorescent material of one device is unnecessarily excitedby the emission from another device.

[0446] According to the embodiment, the emission wavelength becomesfairly stabilized because the primary light from the element isconverted into the secondary light. The wavelength of the resultantsecondary light is not affected by the fluctuation of the wavelength ofthe primary emission. Accordingly, the wavelength of the secondary lightis independent to the operating current or voltage applied to theelement.

[0447] Next explained are specific examples of the embodiment. In theexplanation of these examples, the same components as those of the lightemitting device shown in FIGS. 1 through 89 are labeled with commonreference numerals, and their detailed explanation is omitted.

[0448]FIGS. 90A and 90B are a roughly illustrated plan view and across-sectional view of a-second example of the light emitting deviceaccording to the embodiment respectively. The light emitting device 450Jshown here is a device of a meter needle type. The layer FL includingthe fluorescent material is formed on the light extraction part of thedevice by any method as described above.

[0449]FIG. 91 is a roughly illustrated cross-sectional view of a thirdexample of the light emitting device according to the embodiment. Thelight emitting device 500J shown here is a device of a seven segmenttype of a substrate type. The layer FL including the fluorescentmaterial is formed on the light extraction part of the device by anymethod as described above. The embodiment can also be applied to thedevice of a resin mold type in addition to the cavity type illustratedin the figure.

[0450]FIG. 92 is a roughly illustrated cross-sectional view of a forthexample of the light emitting device according to the embodiment. Thelight emitting device 550J shown here is a device of a seven segmenttype of a lead frame type. The layer FL including the fluorescentmaterial is formed on the light extraction part of the device by anymethod as described above.

[0451]FIG. 93 is a roughly illustrated cross-sectional view of a fifthexample of the light emitting device according to the embodiment. Thelight emitting device 650J shown here is a device of a matrix type. Thelayer FL including the fluorescent material is formed on the lightextraction part of the device by any method as described above.

[0452]FIG. 94 is a roughly illustrated cross-sectional views of a sixthexample of the light emitting device according to the embodiment. Thelight emitting device 700J shown here is a device of an array type. Thelayer FL including the fluorescent material is dispersed in the rod lens740. Alternatively, the layer FL can be coated on the surface of thelens 740, a film including the fluorescent material can be sticked onthe lens 740.

[0453]FIG. 95 is a roughly illustrated cross-sectional view of a seventhexample of the light emitting device according to the embodiment. Thelight emitting device 750J shown here is a laser device of a can type.The layer FL including the fluorescent material is formed on the lightextraction part, i.e. the window of the cap, of the device by any methodas described above.

[0454] The above explained specific examples shown in FIGS. 90 through95 also have various advantages as explained with reference to FIG. 89.

[0455] Next explained is a twelfth embodiment of the invention.According to the embodiment, a piece including the fluorescent materialis placed near the light extraction part of the light emitting element.

[0456] In the following explanations, the same components as those ofthe light emitting device shown in FIGS. 1 through 95 are labeled withcommon reference numerals, and their detailed explanation is omitted.

[0457]FIG. 96A is a roughly illustrated cross-sectional view of aexample of the light emitting device according to the embodiment. Thelight emitting device 100K shown here is an LED lamp of the lead frametype. According to the embodiment, a planar piece FL including thefluorescent material is place above the light extraction part of thelight emitting element 990, which absorbs the primary light emitted fromthe element 990 and emits the secondary light.

[0458]FIG. 96B is a roughly illustrated cross-sectional view of a secondexample of the light emitting device according to the embodiment. Thelight emitting device 100L shown here is also an LED lamp of the leadframe type. In the example, a planar piece FL1 including the fluorescentmaterial is place above the light extraction part of the light emittingelement 990. Besides, another piece FL2 is placed to enclose the spacebetween the element 990 and the piece FL1. The piece FL2 also includesthe fluorescent material and has a cylindlycal shape with a hollow, forexample.

[0459] The pieces FL, FL1 and FL2 according to the embodiment can beformed by sintering a mixed material consisting an appropriate mediumand the fluorescent material. As such a medium, orgamic material orinorganic material can be used. The fluorescent material is dispersed inthe medium. The shapes and the locations of the pieces FL, FL1 and FL2may be appropriately decided depending to the construction of the lightemitting device. These pieces FL, FL1 and FL2 also absorb the primarylight emitted from the element 990 and emit the secondary light.Accordingly, the same advantages as explained fifth reference to theabove embodiments can be obtained as well.

[0460] In the above-explained first through twelfth embodiments withreference to FIGS. 1 through 96B, the light emitting elements and thelight emitting devices including a fluorescent material as a wavelengthconverter are disclosed.

[0461] Next explained are further advanced elements and devices. In thefollowing explanation of thirtieth through twenty-sixth embodiments withreference to FIGS. 97 through 125, various elements and devices having alight absorber and/or a optical reflector in addition to the wavelengthconverter will be disclosed.

[0462]FIG. 97 is a cross-sectional view schematically showing asemiconductor light emitting element taken as the thirtieth embodimentof the invention. The semiconductor light emitting element 2010A shownhere is a semiconductor light emitting element including a wavelengthconverter FL and light absorber AB aligned along the path for extractingthe light. The light emitting layer employed here may be of any kind ofmaterial which can emit a primary light having desired wavelength forthe wavelength converter FL. For example, gallium nitride, siliconcarbide (SiC) or zinc selenide (ZnSe) may be employed as the material ofthe light emitting layer to obtain the primary light of blue or violetwavelength range. The following description shows exemplary cases havinga gallium nitride light emitting layer.

[0463] The light emitting element 2010A may have a multi-layeredstructure of semiconductors stacked on a sapphire substrate 2012,namely, a buffer layer 2014, n-type contact layer 2016, n-type claddinglayer 2018, light emitting layer 2020, p-type cladding layer 2022 andp-type contact layer 2024 which are stacked in this order on thesapphire substrate 2012. These layers may be grown by MOCVD(metal-organic chemical vapor deposition).

[0464] The buffer layer 2014 may be made of n-type GaN, for example. Then-type contact layer 2016 has a high n-type carrier concentration toensure ohmic contact with the n-side electrode 2034, and its materialmay be GaN, for example. The n-type cladding layer 2018 and the p-typecladding layer 2022 function to confine carriers within the lightemitting layer 2020. The light emitting layer 2020 is a layer in whichemission occurs due to recombination of electric charges injected as acurrent into the light emitting element. The light emitting layer 2020may be made of undoped InGaN, for example, and the cladding layers 2018and 2022 may be made of AlGaN having a larger band gap than the lightemitting layer 2020. The p-type contact layer 2024 has a high p-typecarrier concentration to ensure ohmic contact with the p-side electrode2026, and its material may be GaN, for example.

[0465] Stacked on the p-type contact layer 2024 is the p-side electrode2026 which is transparent to light. Stacked on the n-type contact layer2018 is the n-side electrode 2034. Bonding pads 2032 of Au (gold) arestacked on these electrodes, respectively, so that the wires (not shown)for supplying a operating current to the element be bonded. The surfaceof the element is covered by a passivating film 2030 of silicon oxide,for example.

[0466] Stacked on the p-side electrode 2026 are the wavelength converterFL and light absorber AB, in this order. The wavelength converter FL,among these elements, is explained first.

[0467] The wavelength converter FL functions to absorb the primary lightemitted from the light emitting layer 2020 and to emit secondary lighthaving a longer wavelength. The wavelength converter FL may be a layermade of a predetermined medium containing a fluorescent material. Thefluorescent material absorbs the primary light emitted from the lightemitting layer 2020 and is excited thereby to release a secondary lightwith a predetermined wavelength. For example, if the primary lightemitted from the light emitting layer 2020 is the ultraviolet rayshaving the Wavelength of about 330 nm, the wavelength converter FL maybe configured so that the secondary light wavelength-converted by thefluorescent material has a predetermined wavelength in the visible bandor infrared band. The wavelength of the secondary light can be adjustedby selecting an appropriate fluorescent material. Appropriatefluorescent materials absorbing the primary light in the ultravioletband and efficiently emitting the secondary light are, for example,Y₂O₂S:Eu or La₂O₂S:(Eu,Sm) for mission of red light, (Sr, Ca, Ba,Eu)₁₀(PO₄)₆·Cl₂ for emission of blue light, and 3(Ba, Mg, Eu,Mn)O·8Al₂O₃ for emission of green light. By mixing these fluorescentmaterials by an appropriate ratio, substantially all colors in thevisible band can be expressed.

[0468] Most of these fluorescent materials have their absorption peaksin the wavelength band of about 300 to 380 nm. Therefore, in order toensure efficient wavelength conversion by the fluorescent materials, thelight emitting layer 2020 is preferably designed to emit ultravioletrays in the wavelength band below 380 nm. For maximizing the conversionefficiency by the fluorescent materials, the light emitting layer ismore preferably designed to emit ultraviolet rays of a wavelength near330 nm.

[0469] Next explained is the light absorber AB. The light absorber ABhas a wavelength selectivity to absorb the primary light with a highefficiency and to pass secondary light. That is, the light absorber ABhas absorption characteristics in which the absorptance is high to thelight lath the wavelength of the primary light, and low to the lightwith the wavelength of the secondary light. The light absorber AB withsuch characteristics can be made of an absorber dispersed in atranslucent medium. Absorbers usable here are, for example,benzotriazole and cyanoacrylate. P-amino benzoic acid, benzophenone andcinnamic acid may also be usable as the absorber having the similarcharacteristics. Besides, among, the dye materials, cadmium red or redoxide is usable for red secondary light, and cobalt blue or ultramarineblue is usable for blue secondary light.

[0470] By using the light absorber AB, part of the primary light passingthrough the wavelength converter FL1 is absorbed and prevented fromleakage to the exterior. At the same time, the spectrum of extractedlight can be adjusted to improve the chromatic pureness. Additionally,the light absorber AB absorbs ultraviolet rays entering from the outsideof the element and prevents that such external-turbulent lightunnecessarily excites the wavelength converter FL into undesiredemission.

[0471] Next explained is a semiconductor light emitting elementaccording to the fortieth embodiment of the invention.

[0472]FIG. 98 is a cross-sectional view schematically showing thesemiconductor light emitting element according to the fortiethembodiment. Also the semiconductor light emitting element 2010B shownhere may have a gallium nitride compound semiconductor light emittinglayer. In this embodiment, the element has a wavelength converter FL andoptical reflector RE1 along the path for extracting light. The samecomponents as those of the light emitting element shown in FIG. 97 arelabeled With common reference numerals, and their explanation isomitted.

[0473] The embodiment is different from the aforementioned embodimentfor having the optical reflector RE1 instead of the light absorber AB.The optical reflector RE1 is a reflector having a wavelength selectivityand functions to reflect the primary light and pass the secondary lightin the light. That is, the optical reflector RE1 functions as a cut-offfilter or a band-pass filter which reflects light with the wavelength ofthe primary light and passes light with the wavelength of the secondarylight.

[0474] If the primary light is of the ultraviolet wavelength range,titanium oxide (TiO_(x)) or zinc oxide (ZnO_(x)) may be employed to formthe RE1. By dispersing these materials in an appropriate solvent and bycoating it on the wavelength converter FL, the optical reflector RE1 isformed.

[0475] A Bragg reflecting mirror, which can be made by alternatelystacking two kinds of thin films different in refractive index to form areelecting mirror having a high reflectance against light in a specificwavelength band, may be employed as the optical reflector RE1. If thewavelength of the primary light is λ and the optical refractive index ofthe thin film layer is n, a reflecting mirror exhibiting a very highreflectance to the primary light can be made by alternately stacking twokinds of thin films each having the thickness of λ/(4n). These two kindsof thin films preferably have a large difference in optical refractiveindex. Appropriate combinations are, for example, silicon oxide (SiO₂)and titanium oxide (TiO₂); aluminum nitride (AIN) and indium nitride(InN); and a thin film made of any one of these materials and a thinfilm of aluminum gallium arsenide, aluminum gallium phosphide, tantalumpentoxide, polycrystalline silicon or amorphous silicon.

[0476] The optical reflector RE1 made in this manner reflects andreturns part of the primary light passing through the wavelengthconverter FL back to same with a high efficiency. The returned primarylight is then wavelength-converted by the wavelength converter FL andpermitted to pass through the optical reflector RE1 as secondary light.That is, by locating the optical reflector RE1 adjacent to the emissionend of the wavelength converter FL, it is possible to prevent leakage ofthe primary light and to return part of the primary light passingthrough the wavelength converter FL. Therefore, the primary light can beefficiently converted in wavelength. The optical reflector RE1 alsofunctions to reflect ultraviolet rays which undesirably enter into theelement from the outside of the element. It is therefore prevented thatthe wavelength converter FL is excited by external turbulent light intoundesirable emission.

[0477] Next explained is a semiconductor light emitting elementaccording to the fiftieth embodiment of the invention.

[0478]FIG. 99 is a cross-sectional view schematically showing thesemiconductor light emitting element according to the fiftiethembodiment. Also the semiconductor light emitting element 2010C shownhere may have a gallium nitride compound semiconductor light emittinglayer. In this embodiment, the element has a wavelength converter FL, aoptical reflector RE1 and a light absorber AB along the path forextracting light. The same components as those of the light emittingelements shown in FIGS. 97 and 98 are labeled with common referencenumerals, and their explanation is omitted.

[0479] According to the embodiment, by combining the optical reflectorRE1 and the light absorber AB, further improved light emitting elementis realized. That is, the optical reflector RE1 made in this mannerreflects and returns part of the primary light passing through thewavelength converter FL back to same with a high efficiency. Thereturned primary light is then wavelength-converted by the wavelengthconverter FL and permitted to pass through the optical reflector RE1 assecondary light. That is, by locating the optical reflector RE1 adjacentto the emission side of the wavelength converter FL, it is possible toprevent leakage of the primary light and to return the unconvertedprimary light back to the wavelength converter FL. Therefore, theprimary light can be efficiently converted. The optical reflector RE1also functions to reflect ultraviolet rays which undesirably enter intothe element from the outside. It is therefore prevented that thewavelength converter FL is unnecessarily excited by external turbulentlight into undesirable emission.

[0480] In addition to this, by arranging the light absorber AB on theoptical reflector RE1, part of the primary light passing through thereflector RE1 is absorbed and prevented from leakage to the outside. Atthe same time, the spectrum of extracted light can be adjusted toimprove the chromatic pureness. Additionally, the light absorber ABabsorbs ultraviolet rays entering from the exterior and prevents thatsuch external turbulent light excites the wavelength converter FL intoundesired emission.

[0481] Next explained is a semiconductor light emitting elementaccording to the sixtieth embodiment of the invention.

[0482]FIG. 100 is a cross-sectional view schematically showing thesemiconductor light emitting element according to the sixtiethembodiment. Also the semiconductor light emitting element 2010D shownhere may have a gallium nitride compound semiconductor light emittinglayer, and a wavelength converter FL, a optical reflector RE1 and alight absorber AB are arranged along the path for extracting light. Thesame components as those of the light emitting elements shown in FIGS.97 and 98 are labeled with common reference numerals, and theirexplanation is omitted.

[0483] The embodiment shown here further includes a second opticalreflector RE2 on one side of the light emitting layer 2020 nearer to thesubstrate. The optical reflector RE2 functions to reflect the primarylight emitted from the light emitting layer 2020 into the wavelengthconverter FL. Therefore, the primary light emitted from the lightemitting layer 2020 toward the substrate 2012 can be used effectively.When the reflector RE2 is not provided, the primary light from the lightemitting layer 2020 toward the substrate 2012 is absorbed in theinterposed layers or scattered at the bottom surface of the substrate2012, and cannot be converted efficiently in the wavelength converterFL. In the embodiment shown here, however, the optical reflector RE2reflects it and makes it enter into the wavelength converter FL. As aresult, primary light can be converted and extracted externally with ahigher efficiency.

[0484] The optical reflector RE2 may be a Bragg reflecting mirror havinga high reflectance to primary light so that primary light emitted fromthe light emitting layer 2020 toward the substrate 2012 can be returnedback to the wavelength converter FL with a high reflectance. The Braggreflecting mirror may be made by alternately stacking thin films ofaluminum nitride (AIN) and indium nitride (InN), indium nitride andaluminum gallium arsenide, or indium nitride and aluminum galliumphosphide, for example.

[0485] Alternatively, the optical reflector RE2 may be a totalreflection mirror instead of a wavelength selective mirror. That is, byusing a reflecting mirror having a high reflectance to both the primarylight and the secondary light as the optical reflector RE2, anysecondary light departing from the wavelength converter FL toward thesubstrate 2012 can be reflected and extracted efficiently. The totalreflection mirror may be a single-layer metal film, for example, havinga high reflectance, instead of a Bragg reflector.

[0486] The location of the optical reflector RE2 is not limited to theposition shown in FIG. 100, but it may be located either along theboundary of any adjacent two of the crystal layers 2012 through 2020 oron the bottom surface of the substrate 2012. Alternatively, one of thecrystal layers 2014 through 2018 may be used and made as the opticalreflector RE2.

[0487] Next explained is a semiconductor light emitting elementaccording to the seventieth embodiment of the invention.

[0488]FIG. 101 is a cross-sectional view schematically showing thesemiconductor light emitting element according to the seventiethembodiment. Also the semiconductor light emitting element 2010E shownhere includes a wavelength converter FL, optical reflector RE1 and lightabsorber AB along the path for extracting light. Here again, the samecomponents as those of the light emitting element shown in Pigs. 97 and98 are labeled with common reference numerals, and their explanation isomitted.

[0489] The embodiment shown here further includes an optical reflectorRE3 which envelopes the light emitting element. The optical reflectorRE3 may be either a wavelength selective reflector or a total reflectionmirror having no wavelength selectivity.

[0490] When the optical reflector RE3 has a wavelength selectivity, itreflects the primary light emitted from the light emitting layer 2020,and prevents its leakage to the outside. The primary light respectivelyreflected in this manner finally enters into the wavelength converter FLand is converted to the secondary light. Therefore, the wavelengthconversion efficiency is improved. The wavelength selectivity can berealized by using a Bragg reflecting mirror.

[0491] When the optical reflector RE3 has no wavelength selectivity, itprevents external leakage of not only the primary light but also otherwavelength components including secondary light. The total reflectionmirror may be made of a metal film, for example. The total reflectionmirror results in limiting the light emitting path only to an openingwhere the optical reflector RE3 is not made. That is, by covering thesurfaces of the light emitting element 2010C with the optical reflectorRE3 to permit secondary light to be emitted only through a predeterminedopening, the optical radiation pattern can be readily controlled inaccordance with the configuration of the opening. For example, when theoptical reflector RE3 is configured to define a very small opening, alight emitting element as a point light source with a high brightnesscan be made easily. A point light source enables effective convergenceof light by means of an optical means including lenses, and ispractically advantageous in most cases.

[0492] Next explained is a semiconductor light emitting elementaccording to the eightieth embodiment of the invention.

[0493]FIG. 102 is a cross-sectional view schematically showing thesemiconductor light emitting element according to the eightiethembodiment. The semiconductor light emitting element 2010F shown herehas a second optical reflector RE4 which is provided adjacent to theoptical entry side of the wavelength converter FL. That is, the opticalreflector RE4 wavelength converter FL, optical reflector RE1 and lightabsorber AB are provided in this order alone the path for extractinglight. Here again, the same components as those of the light emittingelement shown in FIGS. 97 through 101 are labeled with common referencenumerals, and their explanation is omitted.

[0494] The optical reflector RE4 used in the present embodiment has awavelength selectivity to pass the primary light emitted from the lightemitting layer 2020 and to reflect the secondary light emitted from thewavelength converter after conversion. That is, the optical reflectorRE4 has a low reflectance to the light Kith the wavelength of theprimary light and a high reflectance to the light with the wavelength ofthe secondary light. Such a wavelength selectivity can be realized byusing a Bragg reflecting mirror mentioned before, for example.

[0495] The wavelength converter FL functions to absorb primary light andrelease secondary light with a longer wavelength. Details thereof arethe same as explained with reference to the thirtieth embodiment.

[0496] The optical reflector RE1 is configured to exhibit a low,reflectance to the secondary light emitted from the wavelength converterand a high reflectance to the primary light. Also this type ofwavelength selectivity can be realized by using a Bragg reflectingmirror.

[0497] The light absorber AB is configured to exhibit a high opticalabsorptance to primary light and a low absorptance to secondary light.Structural details thereof may be the same as explained with referenceto the thirtieth embodiment.

[0498] According to the present embodiment, primary light emitted fromthe light emitting layer 2020 passes through the optical reflector RE4,then enters into the wavelength converter FL, and is converted intosecondary light. Part of the primary light passing through thewavelength converter FL without wavelength conversion is reflected bythe optical reflector RE1 back to the wavelength converter FL. Part ofthe primary light not reflected by and passing through the opticalreflector RE1 is absorbed by the light absorber AB not to leak to theoutside.

[0499] Part of the secondary light emitted from the wavelength converterFL and running toward the optical reflector RE1 passes through theoptical reflector RE1 and the light absorber AB, and can be extracted tothe exterior. Part of the secondary light released from the wavelengthconverter FL and running toward the light emitting layer 2020 isreflected by the optical reflector RE4, passes through the wavelengthconverter FL, optical reflector RE5 and light absorber AB, and can beextracted to the outside.

[0500] If the optical reflector RE4 is not provided, secondary lightreleased from the wavelength converter FL toward the light emittinglayer 2020 cannot be efficiently extracted to the outside because themost part thereof is absorbed in the layers 2012 through 2026, orscattered by interfaces of these layers or by the surfaces of thesubstrate. In contrast, according to the embodiment, the opticalreflector RE4 reflects secondary light released from the wavelengthconverter FL toward the light emitting layer 2020 and makes it beefficiently extracted to the outside.

[0501] The present embodiment mall be combined with the sixtiethembodiment or the seventieth embodiment to realize a more efficientsemiconductor light emitting element. When the optical reflector RE2used in the sixtieth embodiment is added to the present embodiment, theprimary light released from the light emitting layer 2020 can be moreefficiently introduced into the wavelength converter FL for wavelengthconversion there. When the optical reflector RE3 used in the seventiethembodiment is added to the present embodiment, the emission aperture ofthe light emitting element is easily controlled and a point-sized lightsource can be made.

[0502] The above explanation with reference to FIGS. 97 through 102 hasbeen made on gallium nitride semiconductor light emitting elements grownon sapphire substrates. However, the invention is not limited to thesespecific examples but similarly applicable to a gallium nitridesemiconductor light emitting element grown on a SiC substrate or anyother appropriate substrate, ensuring the same effects. Materials of thelight emitting layer and other layers are not limited to gallium nitridecompound semiconductors. Any other materials may be used as far as theyensure emission of a primary light which can be efficiently converted inthe wavelength converter FL. In the case where a fluorescent material isused to obtain visible light, the light emitting layer is preferablyconfigured to emit light with a wavelength in bands from blue toultraviolet rays. Usable materials of the light emitting layer of thistype are, ZnSe, ZnS, SiC and BN, for example, in addition to galliumnitride compound semiconductors.

[0503] Next explained are semiconductor light emitting devices accordingto the ninetieth embodiment of the invention.

[0504]FIG. 103 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention. The semiconductor lightemitting device 2 100A shown here is a device called “LED (lightemitting diode) lamp” of a so-called “lead frame type”. The device 2100Aincludes a semiconductor light emitting element 2900 mounted on thebottom of a cup of a lead frame 2110. The p-side electrode and then-side electrode of the light emitting element 2900 are connected tolead frames 2110 and 2120 by wires 2130, 2130, respectively. Inner leadparts of the lead frames are molded in and protected by a resin 2140.

[0505] In the embodiment shown here, a wavelength converter FL islocated on the light emitting element 2900. Further, the resin 2140functions as a light absorber AB which has an wavelength selectivity.

[0506] The wavelength converter FL functions to absorb primary lightemitted from the semiconductor light emitting element 2900 and torelease secondary light with a longer wavelength. Its structure may bethe same as the wavelength converter FL explained with reference to FIG.97. That is, it may be made by dispersing a predetermined fluorescentmaterial in a translucent medium.

[0507] The light absorber AB (resin 2140) has a wavelength selectivityto pass the secondary light and to absorb the primary light. It may bemade by dispersing a predetermined light absorber in the resin 2140.Structural details thereof may be the same as the light absorber ABexplained with reference to FIG. 97. Absorbers usable for theultraviolet primary light are, for example, benzotriazole,cyanoacrylate, p-amino benzoic acid, benzophenone and cinnamic acid asmentioned before.

[0508] The semiconductor light emitting element 2900 is preferably onefor a short emission wavelength in order to increase the conversionefficiency in the wavelength converter FL. The light emitting element ofthis type may be one using gallium nitride compound semiconductors,ZnSe, ZnS, SiC or BN, for example, as the material of the light emittinglayer 2020.

[0509] In the device shown here, since the wavelength converter FL isprovided, primary light from the semiconductor light emitting element2900 is converted into desired visible light or infrared rays.

[0510] Moreover, since the light absorber AB is provided, the primarylight passing through the wavelength converter FL is absorbed andprevented from leakage to the outside, and the spectrum of extractedlight can be adjusted to improve the chromatic pureness. Additionally,the light absorber AB absorbs ultraviolet rays entering from the outsideand prevents that such external turbulent light unnecessarily excitesthe wavelength converter FL into undesired emission.

[0511] The above explanation with reference to FIG. 103 has been made onan LED lamp of a lead frame type. However, the invention is not limitedto these specific example but similarly applicable to an LED lamp of anSMD (surface mount device) type.

[0512] Next explained is a semiconductor light emitting device accordingto the twentieth embodiment of the invention.

[0513]FIG. 104 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention. The device 200B shownhere is also a LED lamp of a lead frame type. In FIG. 104, the samecomponents as those of the light emitting device shown in FIG. 103 arelabeled with common reference numerals, and their explanation isomitted.

[0514] In the embodiment, the wavelength convertor FL is located on thelight emitting element 2900. The resin 2140 is composed of the innermold part 2140 a and the outer mold part 2140 b. The inner mold part 140a is located inside the cup region of the lead frame 110 and functionsas the light absorber AB having a wavelength selectivity. The inner moldpart 2140 a may be made of epoxy resin. The absorber dispersed thereinmay be benzotriazole and so on as explained with reference to FIG. 103.The outer mold part 2140 b is preferably made of a translucent materialto the secondary light.

[0515] A specific example of the fabricating the device is explainedbelow. A fluorescent material having the desired wavelength conversionfunction dispersed in a desired solvent or a coating material and coatedon the surface of the light emitting element 2900. A absorber having thewavelength selectivity is dispersed in a resin and molded into the cupregion of the lead frame 2110 to form the inner mold part 2140 a. Then,a optically transparent resin is applied around the inner mold part toform the outer mold part 2140 b.

[0516] Alternatively, a desired matrix such as solvent, coating materialor resin mixed with the fluorescent material and the absorber may beapplied into the cup region of the lead frame 2110. By utilizing thedifference of the segregating speed between the fluorescent material andthe absorber, the fluorescent layer FL and the light absorber AB may bestacked on the light emitting element in this order. The fluorescentmaterials used in the invention segregates first because they have lagerspecific gravities than the light absorbers. The light absorber tends toremain in the matrix because of their high viscosity. By selecting thelight absorber so that its melting temperature is similar to the curingtemperature of the matrix, the absorber may be uniformly dispersed inthe matrix by performing the curing process.

[0517] Since the light absorber AB is provided, the primary lightpassing through the wavelength converter FL is absorbed and preventedfrom leakage to the outside, and the spectrum of extracted light can beadjusted to improve the chromatic pureness. Additionally, the lightabsorber AB absorbs ultraviolet rays entering from the outside andprevents that such external turbulent light unnecessarily excites thewavelength converter FL into undesired emission.

[0518] Next explained is a semiconductor light emitting devicesaccording to the twenty-first embodiment of the invention.

[0519]FIG. 105 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention. The device 2100C shownhere is also a LED lamp of a lead frame type. In FIG. 106, the samecomponents as those of the light emitting device shown in FIG. 105 arelabeled with common reference numerals, and their explanation isomitted.

[0520] The resin 2140 functions as the optical reflector RE1 having awavelength selectivity. For example, the resin 2140 is made of epoxyresin in which a optical reflector having a wavelength selectivity isdispersed. The reflector dispersed in the resin functions to reflect theprimary light and pass the secondary light in the light entering fromthe wavelength converter FL. If the primary light is of the ultravioletwavelength range, titanium oxide (TiO_(x)) or zinc oxide (ZnO_(x)) maybe employed to form the RE1 as explained above.

[0521] The optical reflector RE1 made in this manner reflects andreturns part of the primary light passing through the wavelengthconverter FL back to same Keith a high efficiency. The returned primarylight is then converted by the wavelength converter FL and permitted topass through the optical reflector RE1 as secondary light. That is, bylocating the optical reflector RE1 adjacent to the emission end of thewavelength converter FL, it is possible to prevent leakage of theprimary light and to return part of the primary light passing throughthe wavelength converter FL. Therefore, the primary light can beefficiently converted in wavelength. The optical reflector RE1 alsofunctions to reflect ultraviolet rays which undesirably enter into theelement from the outside of the element. It is therefore prevented thatthe wavelength converter FL is excited by external turbulent light intoundesirable emission.

[0522] Next explained is a-semiconductor light emitting devicesaccording to the twenty-second embodiment of the invention.

[0523]FIG. 106 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention. The device 2100D shownhere is also a LED lamp of a lead frame type. In FIG. 106, the samecomponents as those of the light emitting device shown in FIG. 103 arelabeled with common reference numerals, and their explanation isomitted.

[0524] In the device shown here, the wavelength convertor FL is locatedon the light emitting element 2900. The resin 2140 is composed of theinner mold part 2140 a and the outer mold part 2140 b. The inner moldpart 2140 a is located inside the cup region of the lead frame 110 andfunctions as the optical reflector RE1 having a wavelength selectivity.

[0525] The inner mold part 2140 a may be made of epoxy resin. Thereflector dispersed therein may be titanium oxide (TiO_(x)) and so on asexplained with reference to FIG. 10D. The outer mold part 2140 b ispreferably made of a translucent material to the secondary light.

[0526] A specific example of the fabricating the device may beessentially the same as explained with reference to FIG. 106. Afluorescent material having the desired wavelength conversion functiondispersed in a desired solvent or a coating material and coated on thesurface of the light emitting element 2900. A reflector having thewavelength selectivity is dispersed in a resin and molded into the cupregion of the lead frame 2110 to form the inner mold part 2140 a. Then,a optically transparent resin is applied around the inner mold part toform the outer mold part 2140 b.

[0527] Alternatively, a desired matrix such as solvent, coating materialor resin mixed with the fluorescent material and the reflector may beapplied into the cup region of the lead frame 2110. By utilizing thedifference of the segregating speed between the fluorescent material andthe reflector, the fluorescent layer FL and the optical reflector RE1may be stacked on the light emitting element in this order.

[0528] By locating such an optical reflector RE1, various advantages asexplained with reference to FIG. 105 can be achieved as well.

[0529] Next explained is a semiconductor light emitting devicesaccording to the twenty-third embodiment of the invention.

[0530]FIG. 107 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention. The device 2100E shownhere is also a LED lamp of a lead frame type. In FIG. 107, the samecomponents as those of the light emitting device shown in FIG. 106 arelabeled with common reference numerals, and their explanation isomitted.

[0531] In the device shown here, the wavelength convertor FL is locatedon the light emitting element 2900. The details about the convertor FLmay be the same as described with reference to FIG. 103. Above theconvertor FL, the light absorber AB is located and the resin 2140 buriesthe inner lead part.

[0532] The light absorber AB in the embodiment also has a wavelengthselectivity to absorb the primary light with a high efficiency and topass the secondary light. A dichroic filter or a ultraviolet-cut filtercan be employed as the absorber AB. The space between the light emittingelement and the absorber AB may be either filled with appropriatematerial such as resin or filled with appropriate gas.

[0533] By locating such an light absorber AB, various advantages asexplained with reference to FIG. 103 can be achieved as well.

[0534] Next explained is a semiconductor light emitting devicesaccording to the twenty-forth embodiment of the invention.

[0535]FIG. 108 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention. The device 2100F shownhere is also a LED lamp of a lead frame type. In FIG. 108, the samecomponents as those of the light emitting device shown in FIG. 103 arelabeled with common reference numerals, and their explanation isomitted.

[0536] In the device shown here, the wavelength convertor FL is locatedon the light emitting element 2900. The details about the convertor FLmay be the same as described with reference to FIGS. 103 through 107.Above the convertor FL, the optical reflector RE1 is located and theresin 2140 buries the inner lead part.

[0537] The optical reflector RE1 in the embodiment also has a wavelengthselectivity to absorb the primary light with a high efficiency and topass the secondary light. A dichroic mirror can be employed as thereflector REB. The Bragg reflector as explained above may also beemployed as the reflector RE1. The space between the light emittingelement and the reflector RE1 may be either filled with appropriatematerial such as resin or filled with appropriate gas.

[0538] By locating such an optical reflector RE1, various advantages asexplained with reference to FIG. 105 can be achieved as well.

[0539] Next explained is a semiconductor light emitting devicesaccording to the twenty-fifth embodiment of the invention.

[0540]FIG. 109 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention. The device 2100G shownhere is also a LED lamp of a lead frame type. In FIG. 109, the samecomponents as those of the light emitting device shown in FIGS. 103through 108 are labeled with common reference numerals, and theirexplanation is omitted.

[0541] In the device shown here, the light emitting element 2900 a is asemiconductor light emitting element which emits light of the wavelengthrange of blue or violet. Generally, in the semiconductor elements ofthis wavelength range, the emission takes place by the energy transitionthrough the impurity level. As a result, the emission spectrum extendsto the ultraviolet wavelength range in most cases. That is, the emittedlight includes ultraviolet component to some extent in addition to thedesired blue or violet light. For example, LEDs made of the galliumnitride compound, zinc selenide, silicon carbide or boron nitride showthis phenomenon.

[0542] According to the embodiment, the inner mold part 2140 a functionsas the light absorber AB. That is, the light absorber AB absorbs theultraviolet component and passes the desired blue or violet light. As aresult, the leakage of the harmfull ultraviolet component is efficientlyprevented and the desired blue or violet light can be extractedsuccessfully. The details of the light absorber AB is as explainedabove. Instead of the inner mold part 2140 a, the outer mold part 2140 bmay be configured to function as the light absorber AB as well.

[0543] Next explained is a semiconductor light emitting devicesaccording to the twenty-sixth embodiment of the invention.

[0544]FIG. 110 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention. The device 100H shownhere is also a LED lamp of a lead frame type. In FIG. 110, the samecomponents as those of the light emitting device shown in FIGS. 103through 109 are labeled with common reference numerals, and theirexplanation is omitted.

[0545] In the device shown here, the light emitting element 2900 a isalso a semiconductor light emitting element which emits light of thewavelength range of blue or violet. The details about the element 2900 amay be the same as described with reference to the FIG. 109. On theelement 2900 a, the light absorber AB having a wavelength selectivity islocated and molded by the resin 2140.

[0546] The light absorber AB absorbs the ultraviolet component emittedfrom the element 2900 a and passes the desired blue or violet light. Adichroic filter or a UV (ultraviolet)-cut filter may be employed as theabsorber AB. The space between the light emitting element and thereflector RE1 may be either filled fifth appropriate material such asresin or filled with appropriate gas.

[0547] By locating such a light absorber AB, various advantages asexplained with reference to FIG. 109 can be achieved as well.

[0548] Next explained is a semiconductor light emitting devicesaccording to the twenty-seventh embodiment of the invention.

[0549]FIG. 111 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention. The device 21001 shownhere is also a LED lamp of a lead frame type. In FIG. 111, the samecomponents as those of the light emitting device shown in FIGS. 103through 110 are labeled With common reference numerals, and theirexplanation is omitted.

[0550] In the device shown here, the light emitting element 2900 a isalso a semiconductor light emitting element which emits light of thewavelength range of blue or violet. The inner mold part 2140 a functionsas the optical reflector RE1 having a wavelength selectivity. That is,the reflector RE1 reflects the ultraviolet component emitted from theelement 2900 a and passes the desired blue or violet light. As a result,the leakage of the harmful ultraviolet component is efficientlyprevented and the desired blue or violet light can be successfullyextracted. The details of the reflector RE1 is as explained withreference to FIG. 105. In addition to the inner mold part 2140 a, theouter mold part 2140 b may also be configured to function as thereflector RE1 as well.

[0551] Next explained is a semiconductor light emitting devicesaccording to the twenty-eighth embodiment of the invention.

[0552]FIG. 112 is a roughly illustrated cross-sectional view of asemiconductor device according to the invention. The device 2100J shownhere is also a LED lamp of a lead frame type. In FIG. 112, the samecomponents as those of the light emitting device shown in FIGS. 103through 111 are labeled with common reference numerals, and theirexplanation is omitted.

[0553] In the device shown here, the light emitting element 2900 a isalso a semiconductor light emitting element which emits light of thewavelength range of blue or violet. On the element 2900 a, the opticalreflector RE1 having a wavelength selectivity is located and the resin2140 is molded.

[0554] The reflector RE1 reflects the ultraviolet component emitted fromthe element 2900 a and passes the desired blue or violet light. Adichroic mirror or a UV (ultraviolet)-cut mirror may be employed as thereflector RE1. The space between the light emitting element and thereflector RE may be either filled fifth appropriate material such asresin or filled With appropriate gas.

[0555] By locating such an optical reflector RE1, various advantages asexplained with reference to FIG. 111 can be achieved as well.

[0556] With reference to FIGS. 103 through 112, the lead frame type LEDlamps are exemplarily shown. However, the invention is not limited tothese specific examples. In addition to these, the invention can beadvantageously applied to the LED lamps of SMD (surface mount device)type or any other various kinds of light emitting devices as well.

[0557] Next explained is a semiconductor light emitting device accordingto the twenty-ninth embodiment of the invention.

[0558]FIG. 113 is a roughly illustrated cross-sectional view of asemiconductor device according to the twenty-ninth embodiment of theinvention. The semiconductor light emitting device 2100K shown here isalso an LED lamp of a lead frame type. In FIG. 113, the same componentsas those of the light emitting device shown in FIGS. 103 through 112 arelabeled with common reference numerals, and their explanation isomitted.

[0559] In the embodiment shown here, a wavelength converter FL and anoptical reflector RE1 are located adjacent to the emission end of thesemiconductor light emitting element 2900. The resin 2140 functions asan light absorber AB having a wavelength selectivity.

[0560] The wavelength converter FL functions to absorb primary lightemitted from the semiconductor light emitting element 2900 and torelease secondary light with a longer wavelength. Its structure may bethe same as the wavelength converter FL explained with reference to FIG.97. That is, it may be made by dispersing a predetermined fluorescentmaterial in a translucent medium.

[0561] The optical reflector RE 1 has a wavelength selectivity toreflect primary light emitted from the semiconductor light emittingelement 2900 and to pass secondary light after conversion by thewavelength converter FL. Here again, its structure may be the same asthe optical reflector RE1 explained with reference to FIG. 98.

[0562] The light absorber AB has a wavelength selectivity to passsecondary light and to absorb primary light. It may be made bydispersing a predetermined light absorber in the resin 2140. Structuraldetails thereof may be the same as the light absorber AB explained withreference to FIG. 97.

[0563] The semiconductor light emitting element 2900 is preferably onefor a short emission wavelength in order to increase the wavelengthconversion efficiency in the wavelength converter FL. The light emittingelement of this type may be one using gallium nitride compoundsemiconductors, ZnSe, ZnS, SiC or BN, for example, as the material ofthe light emitting layer.

[0564] In the device shown here, since the wavelength converter FL isprovided, primary light from the semiconductor light emitting element2900 is converted into desired visible light or infrared rays. Moreover,since the optical reflector RE 1 is provided, part of the primary lightwhich leaks through the wavelength converter FL is reflected with a highefficiency and returned back to the wavelength converter FL. The primarylight returned back in this manner is wavelength-converted in thewavelength converter FL, and then passes through the optical reflectorRE1 as secondary light. That is, by locating the optical reflector RE1adjacent to the emission end of the wavelength converter FL, it ispossible to prevent leakage of the primary light and to return primarylight passing through the wavelength converter FL for wavelengthconversion once again. Therefore, primary light can be converted veryefficiently.

[0565] Furthermore, since the light absorber AB is provided, primarylight passing through the optical reflector RE1 is absorbed andprevented from leakage to the exterior, and the spectrum of extractedlight can be adjusted to improve the chromatic pureness.

[0566]FIG. 114 is a cross-sectional schematic view of the secondsemiconductor light emitting device according to the present embodiment.The semiconductor light emitting device 2150A shown here is a devicecalled “surface mounted lamp (SMD lamp)”. The SMD lamp 2150A includes asemiconductor light emitting element 2900 mounted on a packaging surfaceof a packaging member and protected by a resin 2190. Also in the SMDlamp 2150A of a substrate type shown in FIG. 114, by providing thewavelength converter FL, optical reflector RE1 and light absorber AB,the same effects as explained with reference to FIG. 113 can beobtained. Although the light absorber AB is illustrated as being theresin 2190 itself, it may be another thin film stacked on the surface ofthe resin.

[0567]FIG. 115 is a cross-sectional schematic view of the thirdsemiconductor light emitting device according to the present embodiment.The semiconductor light emitting device 2200A shown here is a “surfaceemission type” semiconductor light emitting device. The surface emissiontype device 2200A includes semiconductor light emitting elements 2900mounted on lead frames 2210 and 2212, respectively, and molded in aresin 2240 within a cup of the reflection plate 2220.

[0568] Light emitted from each semiconductor light emitting element isreflected by the reflection plate 2220, and extracted as wide-spreadlight to the exterior.

[0569] Also in the surface emission type semiconductor light emittingdevice 2200A shown in FIG. 115, by providing the wavelength converterFL, optical reflector RE 1 and light absorber AB, the same effects asthose of the semiconductor light emitting device explained withreference to FIG. 113 can be obtained.

[0570]FIG. 116 is a cross-sectional schematic view of the fourthsemiconductor light emitting device according to the present embodiment.The semiconductor light emitting device 2250A shown here is a devicecalled “dome type”. The dome type device 2250A has a plurality ofsemiconductor elements 2900, e.g. five to ten elements 2900, which aremounted on a lead frame 2260. These semiconductor light emittingelements are connected, respectively, to terminals of the lead frame2260 by shires (not shown), and are molded in an encapsulating resin2290.

[0571] The dome type semiconductor light emitting device 2250 having anumber of semiconductor light emitting elements is advantageous in highluminance and in releasing uniformly spread light.

[0572] Also in the dome type semiconductor light emitting device 2250A,by using the wavelength converter FL, optical reflector RE 1 and opticalabsorber AB, the same effects as those of the semiconductor lightemitting device shown in FIG. 113 can be obtained.

[0573]FIG. 117 is a schematic view of the fifth semiconductor lightemitting device according to the present embodiment. The semiconductorlight emitting device 2300A shown here is a device called “7 segmenttype”, and more particularly, “substrate type”. The central part thereofis illustrated here in a cross-sectional view. The “7 segment type lightemitting device” is a light emitting device for display of numerals.That is, a semiconductor light emitting element 2900 is mounted on asubstrate 2310. Light emitted from the semiconductor light emittingelement 2900 is reflected by a reflection plate 2320.

[0574] Also in the 7 segment type semiconductor light emitting device2300A shown in FIG. 117, by using the wavelength converter FL, opticalreflector RE1 and light absorber AB, the same effects as those of thesemiconductor light emitting device shown in FIG. 113 are obtained.

[0575]FIG. 118 is a schematic view of the sixth semiconductor lightemitting device according to the present embodiment. Also thesemiconductor light emitting device 2350A shown here is a 7 segment typesemiconductor light emitting device, and more particularly, a devicecalled “lead frame type”. The central part thereof is illustrated herein a cross-sectional view. That is, the device includes a semiconductorlight emitting element 2900 mounted on a lead frame 2360 and connectedappropriately by a wire. The semiconductor light emitting element 2900is sealed by a resin 2390. Light emitted from the semiconductor lightemitting element 900 is reflected by a reflection plate 2370 and can beextracted to the exterior.

[0576] Also in the 7 segment type semiconductor light emitting device2350A shown in FIG. 118, by using the wavelength converter FL, opticalreflector RE1 and light absorber AB, the same effects as those of thesemiconductor light emitting device shown in FIG. 113 can be obtained.

[0577]FIG. 119 is a schematic view of the seventh semiconductor lightemitting device according to the present embodiment. The semiconductorlight emitting device 2400A whose central part is shown here in across-sectional view is a semiconductor light emitting device called“LED array type”, “meter indicator type”, “level meter type” or “matrixtype”. The semiconductor light emitting device 2400A includes aplurality of semiconductor light emitting elements mounted inpredetermined intervals on a substrate or a lead frame 2410 andconnected to terminals by wires (not shown). These semiconductor lightemitting elements are molded in an encapsulating resin 2440.

[0578] The semiconductor light emitting device 2400A is compact andlight, and has the advantage of releasing highly luminous anduniform-spread light because a number of semiconductor light emittingelements are mounted.

[0579] Also in the semiconductor light emitting device 2400A shown inFIG. 119, by using the wavelength converter FL, optical reflector RE1and light absorber AB, the same effects as those of the semiconductorlight emitting device shown in FIG. 113 can be obtained. The wavelengthconverter FL is illustrated here as being mixed in the encapsulatingresin 2440; however, it may be a fluorescent layer stacked on surfacesor around the semiconductor light emitting elements.

[0580] If some wavelength converters FL are aligned to release differentkinds of secondary light of different wavelengths, a distribution ofemission colors can be made easily on the indicator. In this case, thepresent invention can realize it only by changing the material of thefluorescent layer while using identical materials and structure forsemiconductor elements, and therefore has the advantage that commondriving current or supply voltage may be applied to all semiconductorelements.

[0581]FIG. 120 is a schematic view of the eighth semiconductor lightemitting device according to the present embodiment. The semiconductorlight emitting device 24D0A shown here in a cross-sectional view is aso-called “can type” semiconductor light emitting device having asemiconductor light emitting element 2900 attached to an end of a stem2470. The semiconductor light emitting element 2900 is a laser element.A photodetector 2475 for monitoring purposes is located behind thesemiconductor light emitting element to monitor optical outputs from thesemiconductor light emitting element 2900. The head portion of the stem2470 is sealed by a can 2490, and laser light can be extracted through awindow 2492.

[0582] Also in the can type laser semiconductor light emitting deice2450A shown in FIG. 120, by using the wavelength converter FL, opticalreflector RE1 and light absorber AB, the same effects as those of thesemiconductor light emitting device shown in FIG. 113 can be obtained.

[0583] Heretofore, semiconductor light emitting devices according to thetwenty-ninth embodiment of the invention, each using the wavelengthconverter FL, optical reflector RE1 and light absorber AB, wereexplained by way of specific examples shown in FIGS. 113 through 120.

[0584] Next explained is the thirtieth embodiment of the invention inform of a semiconductor light emitting device having a second opticalreflector RE2 as used in seventieth embodiment of the invention.

[0585]FIG. 121 is a schematic cross-sectional view showing thesemiconductor light emitting device according to the thirtiethembodiment of the invention. The semiconductor light emitting device2100L shown here is a “lead frame type” “LED lamp”. Also thesemiconductor light emitting device 2100L shown here has the wavelengthconverter FL, optical reflector RE1 and light absorber AB along the pathfor extracting light from the semiconductor light emitting element 2900.Here again, the same components as those of the light emitting deviceshown in FIG. 103 are labeled with common reference numerals, and theirexplanation is omitted.

[0586] In this embodiment, a second optical reflector RE2 is providedunder the semiconductor light emitting element 2900. The opticalreflector RE2 functions to reflect primary light emitted from thesemiconductor light emitting element 2900 and to guide it into thewavelength converter FL. That is, the optical reflector RE2 makes partof the primary light departing from the semiconductor light emittingelement 2900 toward the lead frame 2110 be used effectively. In a devicewithout the reflector RE2, most of the primary light from thesemiconductor light emitting element 2900 toward the lead frame 2110 israndomly reflected by the mounting surface of the element, and is notguided efficiently to the wavelength converter FL for wavelengthconversion therein. In the embodiment, however, the optical reflectorRE2 reflects the primary light into the wavelength converter FL toensure wavelength conversion of the primary light and extraction thereofwith a high efficiency.

[0587] The optical reflector RE2 may be a Bragg reflecting mirror, forexample, as explained before. That is, by using a Bragg reflectingmirror having a high reflectance to primary light as the opticalreflector RE2, primary light departing from the semiconductor lightemitting element 2900 toward the lead frame 2110 can be returned back tothe wavelength converter FL with a high reflectance. The Braggreflecting mirror may be made by alternately stacking thin films ofaluminum nitride (AIN) and indium nitride (InN); indium nitride andaluminum gallium arsenide; and indium nitride and aluminum galliumphosphide, for example.

[0588] Alternatively, the optical reflector RE2 may be a totalreflection mirror having no wavelength selectivity. When the opticalreflector RE2 is a reflection mirror exhibiting a high reflectance toboth primary light and secondary light, secondary light departing fromthe wavelength converter FL toward the lead frame 2110 can be reflectedand extracted efficiently. The total reflection mirror may be made of asingle-layered metal film, for example, having a high reflectance,instead of a Bragg reflecting mirror.

[0589] The present embodiment is not limited to the LED lamp shown inFIG. 121, but similarly applicable also to various kinds ofsemiconductor light emitting devices show in FIGS. 114 through 120 orany other semiconductor devices using a semiconductor light emittingelement, while ensuring similar effects.

[0590] Next explained is the thirty-first embodiment of the invention inform of a semiconductor light emitting device having a third opticalreflector RE3 around its semiconductor light emitting element, like theseventieth embodiment explained above.

[0591]FIG. 122 is a schematic cross-sectional view of the semiconductorlight emitting device according to the thirty-first embodiment. Thesemiconductor light emitting device 2100M shown here is a “lead frametype” “LED lamp”. Here again, the semiconductor light emitting device2100M has the wavelength converter FL, optical reflector RE1 and lightabsorber AB along the path for extracting light from the semiconductorlight emitting element 2900. Here again, the same components as those ofthe light emitting device shown in FIG. 113 are labeled with commonreference numerals, and their explanation is omitted.

[0592] The embodiment shown here further includes a third opticalreflector RE3 around the semiconductor light emitting element 2900. Theoptical reflector RE3 may be either a wavelength selective reflector ora total reflection mirror having no wavelength selectivity.

[0593] When the optical reflector RE3 has a wavelength selectivity,primary light from the semiconductor light emitting element 2900 can bereflected and prevented from external leakage. Primary light reflectedagain and again is finally introduced into the wavelength converter FLad converted into secondary light therein. Therefore, the wavelengthconversion efficiency is improved. The wavelength selectivity can berealized by using a Bragg reflecting mirror as explained before.

[0594] When the optical reflector RE3 has no wavelength selectivity, itprevents leakage of not only primary light but also other opticalcomponents having wavelengths of secondary light, etc. Such a totalreflection mirror may be made of a metal film, for example. By makingthe total reflection mirror, it is possible to limit the path forreleasing light in the light emitting device 2100M to an opening made inthe optical reflector RE3. That is, when the optical reflector RE3covers surfaces of the light emitting device 2100M except the opening topermit secondary light to pass only through the opening, the radiationpattern of light can be controlled easily in accordance with theconfiguration of the opening. For example, when the opening of theoptical reflector RE3 is very small, the semiconductor light emittingdevice is readily made as a point-sized light source. Such a point-sizedlight source is practically advantageous in most cases because light canbe effectively collected by an optical system including lenses amongothers.

[0595] Here again, the embodiment is not limited to the LED lamp shownin FIG. 122 but similarly applicable also to various kinds ofsemiconductor light emitting devices explained with reference to FIGS.114 through 120 and any other semiconductor light emitting devices usingsemiconductor light emitting elements, while ensuring similar effects.

[0596] Next explained is the thirty-second embodiment of the invention.

[0597] In this embodiment, a fourth optical reflector RE4 is interposedbetween the semiconductor light emitting element 2900 and the wavelengthconverter FL, like the eighteenth embodiment explained before.

[0598]FIG. 123 is a schematic cross-sectional view of the semiconductorlight emitting device according to the thirty-second embodiment. Thesemiconductor light emitting device 100N shown here is a “lead frametype” “LED lamp” having the optical reflector RE4, wavelength converterFL, optical reflector RE1 and light absorber AB located in this orderalong the path for extracting light from the semiconductor lightemitting element 2900. Here again, the same components as those of thelight emitting device shown in FIG. 113 are labeled Keith commonreference numerals, and their explanation is omitted.

[0599] The optical reflector RE4 used in the present embodiment has awavelength selectivity to pass primary light from the semiconductorlight emitting element 2900 and to reflect secondary light released fromthe wavelength converter FL after conversion. That is, the opticalreflector RE4 has a low reflectance to light with the wavelength ofprimarily light and a high reflectance to light with the wavelength ofsecondary light. The wavelength selectivity can be realized by using aBragg reflecting mirror, for example, as explained before.

[0600] The wavelength converter FL functions to absorb primary light andto release secondary light having a longer wavelength. Details thereofare the same as already explained with reference to the thirteenthembodiment.

[0601] The optical reflector RE1 is configured to exhibit a lowreflectance to secondary light from the wavelength converter FL and ahigh reflectance to primary light. Here again, the wavelengthselectivity can be realized by using a Bragg reflecting mirror.

[0602] The light absorber AB is configured to exhibit a high opticalabsorptance to primary light and a low absorptance to secondary light.Here again, details thereof may be the same as explained with referenceto the thirteenth embodiment.

[0603] According to the present embodiment, primary light emitted fromthe semiconductor light emitting element 2900 passes through the opticalreflector RE4, then enters into the wavelength converter FL, and isconverted into secondary light. Part of the primary light, which passesthrough the wavelength converter FL without being converted inwavelength, is reflected b the optical reflector RE1 back to thewavelength converter FL. Part of the primary light passing even throughthe optical reflector RE1 is absorbed in the light absorber AB andprevented from external leakage.

[0604] Optical components running toward the optical reflector RE1 amongthe secondary light released from the wavelength converter FL passthrough the optical reflector RE1 and light absorber AB, and can beextracted to the exterior. Optical components running toward thesemiconductor light emitting element 2900 among the secondary lightreleased from the wavelength converter FL are reflected by the opticalreflector RE4, then pass through the wavelength converter FL, opticalreflector REB1 and light absorber AB, and can be extracted to theexterior.

[0605] In a device without the optical reflector RE4, secondary lightreleased from the wavelength converter FL toward the semiconductor lightemitting element 2900 is absorbed by the semiconductor light emittingelement 2900, or randomly reflected by the mounting surface of thesemiconductor light emitting element 2900, and cannot be extractedeffectively. In the present embodiment, however, since the opticalreflector RE4 is provided, secondary light released from the wavelengthconverter FL toward the semiconductor light emitting element 2900 isreflected by the optical reflector RE4, and can be efficiently extractedto the exterior.

[0606] The instant embodiment may be combined with the thirtiethembodiment or thirty-first embodiment to realize a more efficientsemiconductor light emitting device. That is, by adding the opticalreflector RE2 used in the thirtieth embodiment to the structure of thepresent embodiment, primary light emitted from the semiconductor lightemitting element 2900 can be introduced into the wavelength converter FLfor more efficient wavelength conversion therein. When the opticalreflector RE3 used in the thirty-first embodiment is added to thestructure of the present embodiment, a point-sized light source can bemade easily by controlling the emission pattern of the light emittingdevice.

[0607] Next explained is the thirty-third embodiment of the invention inform of an image display device having a combination of a semiconductorlight emitting element, wavelength converter, optical reflector andlight absorber.

[0608]FIG. 124 is a schematic cross-sectional view of an exemplarystructure of the image display device according to the embodiment. Theimage display device 2500A shown here includes a light source section2520, luminance adjuster 2530 and converter 2550.

[0609] The light source section 2520 includes a semiconductor lightemitting element 2900 lath a predetermined emission spectrum as itslight source, and an optical guide plate 2522 for uniformly spreadinglight from the semiconductor light emitting element 2900 to irradiatethe luminance adjuster.

[0610] The luminance adjuster 2530 is configured to adjust opticaltransmittance by means of a liquid crystal, for example. That is, theluminance adjuster 2530 includes a liquid crystal layer 2536 interposedbetween polarizing plates 2531 and 2539. When a predetermined voltage isapplied across the pixel electrode 2534 and an opposite electrode 2538,the liquid crystal layer 2536 is controlled in orientation of itsmolecules and controls the optical transmittance in cooperation Kith theupper and lower polarizing plates 2531 and 2539. Each pixel electrode2534 formed on a translucent substrate 2532 is supplied with apredetermined voltage via a switching element 2535. The switchingelement 2535 may be a metal-insulator-metal (MIM) bonded element or athin film transistor (TFT) made of hydrogenated amorphous silicon orpolycrystalline silicon, for example.

[0611] The converter 2550 includes wavelength converters FL 1 throughFL3, optical reflectors RE1 through RE3 and light absorbers AB1 throughAB3 under the translucent substrate 2542. The wavelength converters FLmay be partitioned for individual pixels by a black matrix made of alight screen material. The wavelength converters FL may be located overthe translucent substrate 2542.

[0612] In the image display device 2000A, light from the light sourcesection 2520 is adjusted in quantity of light for individual pixels inthe luminance adjuster 2530 in response to the voltage applied to theliquid crystal layer 2536, and enters into the wavelength converters FL1 through FL3. In the wavelength converters FL 1 to FL3, the incidentprimary light is converted into secondary light with predeterminedwavelengths depending upon the natures of respective fluorescentmaterials. For example, the light may be converted to red light in FL1,to green light in FL2 and to blue light in FL3, respectively.

[0613] Secondary light released from the wavelength converters FL1through FL3 enters into the optical reflectors RE1 through RE3. Eachoptical reflector has a wavelength selectivity to reflect primary lightand to pass only secondary light.

[0614] Secondary light passing through the optical reflectors RE1 to RE3enters into the light absorbers AB1 through AB3. Each of the lightabsorbers AB 1 to AB3 has a wavelength selectivity to pass specificsecondary light and to absorb primary light. They may be formed as colorfilters so that, for example, AB1 passes red light, AB2 passes greenlight and AB3 passes blue light.

[0615] According to the invention, since the semiconductor lightemitting element is used as the light source, the photoelectricconversion efficiency is higher than those of conventional cathodefluorescent tubes, and the power consumption can be reduced.Additionally, as a result of employing the novel structure configured toexcite the fluorescent materials by light from the highly efficientsemiconductor light emitting element, the power consumption of theentire image display device can be reduced.

[0616] Especially, in the present invention, by providing the opticalreflectors RE and light absorbers AB in addition to the wavelengthconverters, the conversion efficiency is further improved. Moreover,when the fourth optical reflector RE4 as explained with reference toFit. 102 or FIG. 123 is provided adjacent to incident ends of thewavelength converters FL1 to FL3 in the image display device 2500A,secondary light released from the wavelength converters FL1 through FL3can be reflected and extracted to the exterior with a higher efficiency.

[0617] In a practically prepared device, namely, a 10.4 inch TFT liquidcrystal display device using a conventional cathode fluorescent tube asits light source, the power consumption was about 9 Watt. In contrast,in the image display device according to the invention using anultraviolet LED and a fluorescent material, the power consumption isabout 4 Watts, which is less than a half of the power consumption of theconventional liquid crystal display device. As a result, the inventioncan elongate the life of batteries of portable electronic apparatusessuch as note-type computers or terminal apparatuses of various kinds ofinformation network systems.

[0618] Additionally, according to the invention, since the wavelengthconverters FL can be located nearest to the surface of the image displayscreen, the visual angle is improved significantly.

[0619] It is further possible to simplify the circuit and to reduce thedriving voltage as compared with conventional cathode fluorescent tubes.Cathode fluorescent tubes required a stabilizing circuit and an inverterto apply a high voltage therethrough. In the present invention, however,the semiconductor light emitting element used as the light sourcepromises a sufficient emission intensity with a d.c. voltage as small as2 to 3.5 V, approximately, and the stabilizing circuit and the invertercircuit need not be used. Therefore, the circuit for driving the lightsource can be simplified remarkably, and the driving voltage can bereduced.

[0620] Moreover, according to the invention, the life of the lightsource can be largely elongated than conventional ones. Conventionalcathode fluorescent tubes are subject to a rapid decrease in luminanceand further to no emission after a predetermined life time due tosputtering or other like phenomenon at the electrode portion. In thepresent invention, however, the semiconductor light emitting elementused as the light source maintains the original luminance withoutsubstantial deterioration even after a long use as long as tens ofthousands hours, and its life is approximately eternal. Therefore, theimage display device according to the invention has a remarkably longerlife as compared with conventional devices.

[0621] Additionally, in the image display device according to theinvention, the rising time for operation is very short. The time afterpowering the power source to driving the light source for its normalluminance is remarkably short as compared with conventional cathodefluorescent tubes. That is, the light source operates quickly.

[0622] The present invention improves the reliability as well.Conventional cathode fluorescent tubes have a structure confining a gaswithin a glass tube. Therefore, they are liable to break with shocks orvibrations. In the present invention, however, since the semiconductorlight emitting element used as the light source is a solid statecomponent, the durability against shocks or vibrations is much higher.As a result, the invention significantly improves the reliability ofvarious types of portable electronic apparatuses using image displaydevices.

[0623] Additionally, the present invention does not use harmful mercury.Many of conventional cathode fluorescent tubes contained a predeterminedamount of mercury in the glass tube. The present invention, however,need not use harmful mercury.

[0624] Next explained is a image display device according to thethirty-forth embodiment of the invention.

[0625]FIG. 125 is a schematic cross-sectional view of the modified imagedisplay device according to the thirty-forth embodiment of theinvention. Here again, the image display device 2500B includes the lightsource section 2520, luminance adjuster 2530 and converter 2550. Theimage display device 2500B, however, is different from the image displaydevice 2500A in location of the converter 2550 which is located betweenthe light source 2520 and the luminance adjuster 2530. The samecomponents of the device shown here as those of the image display device2500A are labeled with common reference numerals, and their explanationis omitted.

[0626] In the image display device 2500B, primary light emitted from thesemiconductor light emitting element 2900 enters into the wavelengthconverters FL1 through FL3 via the optical guide plate 2522. Theincident primary light is converted into secondary light havingpredetermined wavelengths in respective wavelength converters, andenters into the optical reflectors RE1 through RE3. Then, primary lightcomponents are reflected, and secondary light components pass them andenter into the light absorbers AB1 through AB3. Also in the lightabsorbers AB1 to AB3, primary light components are absorbed, andsecondary light passes therethrough, ad explained before.

[0627] Also the image display device 2500B shown in FIG. 125 promisesthe same effects as those of the image display device 2500A explainedabove. In the image display device 2000B, primary light, such asultraviolet rays, emitted from the semiconductor light emitting element2900 is wavelength-converted into secondary light with a longerwavelength, and then enters into the luminance adjusters. Therefore,this version overcomes the problem that the switching elements 2535 andthe liquid crystal layer 2536 are exposed to and deteriorated byultraviolet rays as primary light.

[0628] In the above-explained thirteenth through thirty-forthembodiments with reference to FIGS. 97 through 125, the light emittingelements, the light emitting devices and image display device having acombination of a wavelength converter, a light absorber and a opticalreflector are disclosed.

[0629] Next explained are the exemplary products, such as illuminators,projectors or purifiers, which include the light emitting deviceexplained above.

[0630]FIGS. 126A through 126C are schematic diagrams showing an novelilluminator according to an embodiment of the invention. Fit. 126A is aperspective view of the entirely of the illuminator 4100, FIG. 126B is across-sectional view, and FIG. 126C is a schematic plan view of a wiringboard used therein.

[0631]FIG. 126D is a schematic diagram showing the electrical circuit ofthe illuminator 4100.

[0632]FIG. 127 is a schematic diagram showing a conventional fluorescentlamp system. The system 4900 comprises a fluorescent lamp 4910 and apower supply 4920. The fluorescent lamp 4910 has a glass tube 4911 and afluorescent material is coated onto the inner surface of the tube 4911.A mixed gas 49 12 containing a mercury vapor and a inert gas such asargon (Ar) is sealed inside the tube 4911. The power supply 4920 isconnected to the electrodes 4915, 4915 which are located at the oppositeends of the tube 4911. The power supply 4920 generates a alternativevoltage having a high frequency. The voltage is supplied to theelectrodes 4915, 4915 and the mercury vapor generates a glow dischargewhich generates the ultraviolet rays. The emitted UV rays are absorbedin by the fluorescent material 4913 and converted to a visible lightwhich is emitted through the glass tube 4911 to the outside.

[0633] However, the fluorescent system as shown in FIG. 127 requires thepower supply 4920 to be equipped with a circuitry of increasing voltageand generating high frequency to supply the high frequency voltage tothe fluorescent lamp. As a result, the power supply must have acomplicated structure, which increases the cost, deteriorates thereliability and shorten the life of the system.

[0634] Another problem is that the starting speed is slow and the lightpower is unstable just after the starting because the conventionalsystem utilizes the glow discharge of the mercury vapor. Further, theoutput power tends to decrease especially at the lower temperaturebecause the state of the discharge is affected by the ambienttemperature.

[0635] Besides, when the conventional fluorescent lamp is used, it ishard to downsize the system, to improve the life and to improve themechanical durability against the mechanical shock or vibration. It isalso necessary to prevent the environmental pollution by the mercury.

[0636] Another conventional technique widely used for an illuminator isa electric light bulb. However, the conventional light bulb has theglass bulb which seals a hot filament inside. This classicalconstruction also requires many improvements about, for example, powerconsumption, efficiency, the heat generation, life, mechanicalreliability, size, weight, and so on.

[0637] In contrast to these conventional technique, the novelilluminator 4100 according to the invention has drastically improvedconstruction. As shown in FIGS. 126A through 126D, the illuminator 4100includes a showing board 110 contained in shells 120A and 120B. Theshells 4120A and 4120B may be made of a resin, for example. The shell4120A is a translucent cover, and the shell 4120B is used also as a basefor attachment to a ceiling, for example.

[0638] The spiring board 4110 supports an arrangement of semiconductorlight emitting devices 130 for emitting white light. Each semiconductorlight emitting device 4130 includes a light emitting diode (LED) foremitting ultraviolet rays and a fluorescent member as explained later ingreater detail. The semiconductor light emitting devices 4130 preferablyhave “three waveform type” white emission characteristics in which theintensity reaches peaks in red, green and blue wavelength bands, forexample.

[0639]FIG. 128 is a schematic cross-sectional view of a semiconductorlight emitting device 4130 suitable for use in the present embodiment.The semiconductor light emitting device 4130 includes at least asemiconductor light emitting element 4132 and a fluorescent element ( awavelength converter) 4136. The semiconductor light emitting element4132 is mounted on a packaging member 4134 such as lead frame. Thefluorescent element 4136 is disposed on a path for extracting light fromthe semiconductor light emitting element 4132. The semiconductor lightemitting element 4132 may be sealed in a resin 4138, for example.

[0640] The semiconductor light emitting element 4132 releasesultraviolet rays, and the fluorescent element 4136 absorbs theultraviolet rays, converts them in wavelength, and release visible lightor infrared rays of a predetermined wavelength to the exterior.

[0641] The wavelength of light released from the fluorescent element canbe adjusted by selecting an appropriate material therefor. Exemplarfluorescent materials for absorbing ultraviolet rays from thesemiconductor light emitting element 4132 and for efficiently releasingsecondary light are Y₂O₂S:Eu or La₂O₂S:(Eu,Sm) for releasing red light;(Sr, Ca, Ba, Eu)₁₀(PO₄)₆·C₁₂ for releasing blue light; and 3(Ba, Mg, Eu,Mn)O·8Al₂O₃ for releasing green light. By mixing these fluorescentmaterials by an appropriate ratio, almost all colors in visible bandscan be made.

[0642] Most of these fluorescent materials exhibit absorption peaks inwavelength bands around 330 nm. Therefore, in order to ensure efficientwavelength conversion by using these fluorescent materials, thesemiconductor light emitting element 4132 preferably emits ultravioletrays in a wavelength band near 330 nm. The semiconductor light emittingelement 4132 having these characteristics may be obtained by using GaNcontaining boron (B) as its light emitting layer, and its preferablestructure will be explained later in greater detail.

[0643] The fluorescent element 4136 may be provided in a locationdistant from the semiconductor light emitting element 4132 along thepath for emitting light therefrom or may be stacked on the surface ofthe semiconductor light emitting element 4132. Alternatively thefluorescent element 4136 may be disposed or contained within thesemiconductor light emitting element 4132.

[0644] Returning, back to FIG. 126A through 126D, semiconductor lightemitting devices 4130 are arranged in predetermined intervals on themajor surface of the wiring board 4110 in accordance with requiredconditions, such as quantity of illumination light, size, power, and soon. In order to ensure compact and dense packaging on the substrate4110, semiconductor light emitting devices 4130 are preferablyconfigured as “surface mounted (SMD)” lamps. By miniaturizing individuallight sources in this manner, light from the light sources can becollected by combining optical reflectors with individual light sources,and a highly efficient and bright illuminator can be realized.

[0645] As to mutual connection of semiconductor light emitting devices4130, 4130 packaged on the substrate 4110, it is preferable to makeunits U each containing a predetermined number of serially connectedsemiconductor light emitting devices 4130 and to connect these units Uin parallel as exemplarily shown in FIG. 126D. In the figure, theelement denoted by the numeral 4800 is a power supply.

[0646] If this manner of connection is used, the power source voltageand driving current need not be set high, and, even when a troubleoccurs in one or more of the semiconductor light emitting devices 4130,adverse affection to the other semiconductor light emitting devices4130, such as changes in driving voltage, can be reduced. That is, evenwhen any one or more of the units fall in malfunctions, the other unitscan operate normally. Therefore, unlike the conventional fluorescentlamps, the illuminator shown here is not damaged totally, and is muchmore advantageous in reliability. However, the present invention is notlimited to this, all of the semiconductor light emitting devices 4130 onthe wiring board 4110 may be connected in series or in parallel.

[0647] Although the above-explained example uses semiconductor lightemitting devices 4130 for white emission, the invention is not limitedto it. For example, semiconductor light emitting devices for ultravioletemission may be provided on the wiring board, combining a fluorescentelement stacked on an inner wall surface of a resin cover 4120A, so asto absorb ultraviolet rays, convert them in wavelength and release whitelight to the exterior.

[0648] In order to ensure interchangeability with conventionalfluorescent lamps, it is convenient to provide a converter circuit forconverting an RF driving voltage to be applied to a fluorescent lampinto a d.c. voltage and for supplying, it to the semiconductor lightemitting device 4130. Such a converter circuit may be provided to thesupply 4800 shown in the FL. 126D. The illuminator according to theembodiment is usable in wide applications, such as street lamps, spotlight for the inspection of semiconductor wafers, mask aligning machineor other light sources of various kinds of manufacturing equipments,light sources for plant cultivation, in addition to home-use oroffice-use room lamps.

[0649] According to estimation by the Inventor, semiconductor lightemitting devices 4130 arranged in four lines each containing 66 devices,for example, will be sufficient to obtain a quantity of lightcorresponding to a conventional 40 W fluorescent lamp.

[0650] The illuminator according to the invention is lower in powerconsumption, longer in life, more easily reduced in size and weight, andmechanically much stronger against shocks and vibrations thanconventional fluorescent lamps. Moreover, the problem of environmentalpollution by mercury can be overcome.

[0651] Next explained is the second example of the applied products.

[0652]FIG. 129 is a schematic diagram showing a flashing device for acamera according to the invention. The camera 4150 shown here includes alens 4152, finder 4154 and a semiconductor light emitting device 4130according to the invention as its flash. The semiconductor lightemitting device 4130 releases white light having a predeterminedwavelength distribution by means of a semiconductor light emittingelement and a fluorescent element as explained with reference to FIG.128. Depending on the material of the fluorescent element 4136 used inthe semiconductor light emitting device 4130, it is applicable also toenhancement of a specific emission wavelength or to infrared camera. Thesemiconductor light emitting device 4130 is connected to a pulsegenerator 4158, and behaves as a flash when supplied with a pulsatingdriving current.

[0653] The flash device according to the invention is lower in powerconsumption and longer in life as compared with conventional cameraflashing devices using bulbs. Additionally, using the characteristics ofthe semiconductor light emitting element, the flashing device can beused for special applications, such as ultra-high speed cameras.

[0654] Next explained is the third example of the applied products.

[0655]FIG. 130 is a schematic diagram showing a lamp according to theinvention. The lamp unit 4200 shown here includes a semiconductor lightemitting device 4130 near the focal point of a concave mirror 4210.Within the semiconductor light emitting device 4130, ultraviolet raysemitted from a semiconductor light emitting element iswavelength-converted by a fluorescent element, and released to theexterior as white light, for example. The light is collected andreleased toward a predetermined direction by the concave mirror 4210.The focal power can be improved by concentrating the fluorescentsubstance behaving as the light source near the focal point of theconcave mirror within the semiconductor light emitting device 130.

[0656] The lamp unit 4200 according to the invention is applicable tocar-borne head lamps or flash lamps, for example. The semiconductorlight emitting device 4130 shown here is readily miniaturized ascompared fifth conventional bulbs. I 0 Therefore, the semiconductorlight emitting devices 4130 for different emission colors can be locatedadjacent to the focal point of the concave mirror 4210. As a result, aplurality of emission colors can be made with a single lamp 4200. Forexample, a head lamp and a fog lamp can be incorporated in a common lampunit. It is also possible to combine a back lamp and a stop lamp.

[0657] Instead of using the semiconductor light emitting device 4130, asemiconductor light emitting element 4132 for ultraviolet emission canbe provided so that, after the ultraviolet rays are reflected directlyby the concave mirror 4210, the light be wavelength-converted by afluorescent element. In this case, the fluorescent element may bestacked on the reflecting surface of the concave mirror 4210, or may belocated at the emission window of the lamp unit.

[0658] The device according to the invention is lower in powerconsumption, longer in life and much higher in mechanical strengthagainst vibration and shocks than conventional lamp units using bulbs.Moreover, since the light source can be made small, the focal power isincreased remarkably, and it is especially advantageous for illuminatinga distant object with a high luminance.

[0659] Next explained is the fourth example of the applied products.

[0660]FIG. 131 is a schematic diagram showing a read-out deviceaccording to the invention. The read-out device 4250 shown here includesa semiconductor light emitting device 4130A for emitting red light, asemiconductor light emitting device 4130B for emitting green light and asemiconductor light emitting device 4130C for emitting blue light. Thesesemiconductor light emitting devices 4130A through 4130C can beconfigured to emit light of their respective colors by changing thematerial of the fluorescent element 4136 contained therein.

[0661] Red light, green light and blue light from the semiconductorlight emitting devices 4130A through 4130C are irradiated onto amanuscript, not shown, and reflected rays of these different-coloredrays are detected by photodetectors 4260A through 4260C, respectively.The photodetectors 4260A through 4260C may be photosensitive elements orCCDs (charge coupled devices), for example. The read-out deviceaccording to the invention may be incorporated into a facsimile machine,scanner copy machine to read out information from a manuscript andconvert it into electric signals.

[0662] The device according to the invention is lower in powerconsumption, much longer in life and much higher in mechanical strengthagainst vibration and shocks than conventional read-out devices usingfluorescent lamps.

[0663] Next explained is the fifth example of the applied products.

[0664]FIG. 132 is a schematic diagram showing a projector according tothe invention. The projector 4300 shown here includes a semiconductorlight emitting device 4130 near a focal point of an concave mirror 4310,and a projecting lens 4320 in front of them. Light released from thesemiconductor light emitting device 4130 is collected by the concavemirror 4310, and the transmission pattern of a manuscript drawn onto atranslucent sheet is projected onto a screen 4342 by the projecting lens4320.

[0665] The projector according to the invention is lower in powerconsumption and generated heat, much longer in life, easier for reducingin size and weight, and much higher in mechanical strength againstvibration and shocks than conventional read-out devices using bulbs.

[0666] Next explained is the sixth example of the applied products.

[0667]FIG. 133 is a schematic diagram showing a purifier according tothe invention. The purifier 4350 shown here includes an ozone generator4370 and a semiconductor light emitting element 4132 disposed along apuffing circuit 4360. When water 435A is supplied to the purifyingcircuit 4360, it is sterilized and purified by ultraviolet rays from thesemiconductor light emitting element 4132, and discharged as clean water4355B. If ozone is solved into water by the ozone generator 4370 priorto irradiation of ultraviolet rays, the sterilizing and purifyingeffects is improved because of the sterilization and purification byozone and generation of active oxygen by irradiation of ultravioletrays.

[0668] The purifier 4350 according to the invention is also useful forair purification. When air is supplied to the puriying circuit 4360,ultraviolet rays are irradiated to the air from the semiconductor lightemitting device 4132 to sterilize and purify the air. When a heater, notshown, is added to heat the air and discharge hot air, the sterilizingeffect of the purifier can be increased. The purifier 4350 according tothe invention is applicable for sterilizing and purifying interiors ofmedical appliances storage cases, refrigerators, and so forth.

[0669] The purifier according to the invention is higher in intensity ofultraviolet rays and purifying ability, lower in power consumption, muchlonger in life, and much higher in mechanical strength againstvibrations and shocks than conventional purifiers using ultravioletfluorescent lamps. Moreover, the purifier can operate for itspredetermined stable output immediately after the semiconductor lightemitting element 4132 is turned on. Additionally, since the purifier canbe miniaturized as a whole, it can be set in any location and especiallyuseful in aquariums for decorative fish and home baths to purify water.

[0670] Next explained is the seventh embodiment of the invention.

[0671]FIG. 134 is a schematic diagram of a ultraviolet irradiatoraccording to the seventh embodiment of the invention. The ultravioletirradiator 4400 shown here includes a semiconductor light emittingelement 4132 near the focal point of a concave mirror 4410. Ultravioletrays emitted from the semiconductor light emitting element 132 arereflected and collected by the concave mirror 4410, and irradiated on atarget 4440 with a high irradiation intensity. In this manner, theultraviolet irradiator 4400 can be used for resin molding, sunburningand disinfection, for example. If a BGaN (boron gallium nitride)compound semiconductor light emitting element, explained later, is used,the ultraviolet irradiator 4400 can be used as physiotherapy instrumentsfor generating ultraviolet rays near 300 nm which promote creation ofvitamin D in human bodies.

[0672] The ultraviolet irradiator according to the invention is higherin intensity of ultraviolet rays, lower in power consumption much longerin life and much higher in mechanical strength against vibrations orshocks than conventional ultraviolet irradiators using ultravioletfluorescent lamps. Moreover, since the invention can miniaturize thelight source remarkably, the focal power is increased, and theultraviolet irradiation density can be increased remarkably.

[0673] Next explained is the eighth example of the applied products.

[0674]FIG. 135 is a schematic diagram showing a display device accordingto the invention. The display device 4450 shown here includes asemiconductor light emitting element 4130 for emitting ultraviolet raysand a display panel 4460. On the back surface of the display panel 4460,characters and figures are drown by a plurality of fluorescent elementsdifferent in emission color. Ultraviolet rays emitted from thesemiconductor light emitting element 4132 are converted in wavelength bythe fluorescent elements on the back surface of the display panel 4460and represent patterns of characters and figures.

[0675] Alternatively, a semiconductor light emitting device 4130 may beused instead of the semiconductor light emitting element 4132 forultraviolet emission. In this case, white light or other visible lightemitted from the semiconductor light emitting device 4130 can be used asback light to display characters or figures on the display panel.

[0676] The display device 4450 according to the invention can be used inwide applications, such as car-borne indicator lamps, display lamps oftoys, alarm lamps and emergency lamps, for example.

[0677] The display device according to the invention is higher indisplay brightness, lower in power consumption, much longer in life andmuch higher in mechanical strength against vibrations and shocks thanconventional display devices using fluorescent lamps or bulbs.

[0678] Next explained is the ninth example of the applied products.

[0679]FIG. 136 is a schematic diagram showing a semiconductor lightemitting device according to the invention. The semiconductor lightemitting device 4500 shown here includes a semiconductor light emittingelement 4132 for emitting ultraviolet rays, first optical reflector4510, wavelength converter 4520, second optical reflector 4530 and lightabsorber 4540 formed in this order.

[0680] The first optical reflector 4510 has a wavelength selectivity topass ultraviolet rays from the semiconductor light emitting element 4132and to reflect visible light or other secondary light emitted from thewavelength converter 20 after wavelength conversion. That is, the firstoptical reflector 4510 has a low reflectance to ultraviolet rays fromthe semiconductor light emitting element 4132 and a high reflectance tolight with a wavelength of the secondary light from the wavelengthconverter 4520.

[0681] The wavelength selectivity can be made by using a Braggreflecting mirror, for example. That is, by alternately stacking twokinds of tin films different in refractive index, a reflecting mirrorhaving a high reflectance to light in a particular wavelength band canbe made. For example, when the wavelength of primary light is λ and thephotorefractive index of the thin film layer is n, by alternatelystacking two kinds of thin films each having the thickness of λ/(4n), areflecting mirror having a very high reflectance to primary light can bemade. These two kinds of thin films preferably have a large differencein photorefractive index. Appropriate combinations are, for example,silicon oxide (SiO₂) and titanium oxide (TiO₂); aluminum nitride (AIN)and indium nitride (InN); and a thin film made of any one of thesematerials and a thin film of aluminum gallium arsenide, aluminum galliumphosphide, tantalum pentoxide, polycrystalline silicon or amorphoussilicon.

[0682] The wavelength converter 4520 functions to absorb ultravioletrays from the semiconductor light emitting element 4132 and to releasesecondary light with a longer wavelength. The wavelength converter 4520may be a layer made of a predetermined medium containing a fluorescentelement. The fluorescent element absorbs ultraviolet rays emitted fromthe light emitting element 4132 and is excited thereby to releasesecondary light with a predetermined wavelength. For example, if theultraviolet rays emitted from the light emitting element 4132 have thewavelength of about 330 nm, the wavelength converter 4520 may beconfigured so that the secondary light wavelength-converted by thefluorescent element has a predetermined wavelength in the visible bandor infrared band. The wavelength of the secondary light can be adjustedby selecting an appropriate material as the fluorescent element.Appropriate fluorescent materials absorbing primary light in theultraviolet band and efficiently releasing secondary light are, forexample, Y₂O₂S:Eu or La₂O₂S:(Eu,Sm) for mission of red light, (Sr, Ca,Ba, Eu)₁₀(PO₄)₆·C₁₂ for emission of blue light, and 3(Ba, Mg, Eu,Mn)O˜8Al₂O₃ for emission of green light. By mixing these fluorescentmaterials by an appropriate ratio, substantially all colors in thevisible band can be expressed.

[0683] Most of these fluorescent materials have their absorption peaksin the wavelength band of about 300 to 380 nm. Therefore, in order toensure efficient wavelength conversion by the fluorescent materials, thesemiconductor light emitting element 4132 is preferably configured toemit ultraviolet rays in the wavelength band near 330 nm.

[0684] Next explained is the second optical reflector 4530. The opticalreflector 4530 is a reflective mirror having a wavelength selectivity,and functions to reflect ultraviolet rays and pass secondary light inthe light entering from the wavelength converter 4520. That is, theoptical reflector 4530 behaves as a cut-off filter or a band pass filterwhich reflects light with the wavelength of the ultraviolet rays andpasses light with the wavelength of the secondary light. It may be aBragg reflecting mirror, for example, as explained before.

[0685] The optical reflector 4530 made in this manner reflects andreturns ultraviolet rays passing through the wavelength converter 4520back to same with a high efficiency. The returned ultraviolet rays arethen wavelength-converted by the wavelength converter 4520 and permittedto pass through the optical reflector 4530 as secondary light. That is,by locating the optical reflector 4530 adjacent to the emission end ofthe wavelength converter 4520, it is possible to prevent leakage of theultraviolet rays and to return part of the ultraviolet rays passingthrough the wavelength converter 520. Therefore, the ultraviolet rayscan be efficiently converted in wavelength. The optical reflector 4530also functions to reflect ultraviolet rays which undesirably enter intothe element from the exterior. It is therefore prevented that thewavelength converter 4520 is excited by external turbulent light intoundesirable emission.

[0686] Next explained is the light absorber 4540. The light absorber4540 has a wavelength selectivity to absorb ultraviolet rays with a highefficiency and to pass secondary light. That is, the light absorber 4540has absorption characteristics in which the absorptance is high to lightwith the wavelength of the ultraviolet rays, and low to light with thewavelength of the secondary light. The light absorber 4540 with suchcharacteristics can be made of an absorber dispersed in a translucentmedium. Absorbers usable here are, for example, cadmium red or red oxidefor red secondary light, and cobalt blue or ultramarine blue for bluesecondary light.

[0687] By using the light absorber 4540, part of ultraviolet rayspassing through the optical reflector 4530 is absorbed and preventedfrom leakage to the exterior. At the same time, the spectrum ofextracted light can be adjusted to improve the chromatic pureness.Additionally, the light absorber 4540 absorbs ultraviolet rays enteringfrom the exterior and prevents that such external turbulent lightexcites the wavelength converter 4520 into undesired emission.

[0688] In the device shown here, ultraviolet rays emitted from thesemiconductor light emitting element 4132 enter into the wavelengthconverter 4520 through the first optical reflector 45010 andwavelength-converted into secondary light. Part of the ultraviolet rayspassing through the wavelength converter 4520 without beingwavelength-converted therein is reflected by the second opticalreflector 4530 back to the wavelength converter 520. Part of theultraviolet rays passing even through the optical reflector 4530 isabsorbed by the light absorber 4540 and prevented from external leakage.

[0689] Light components going toward the second optical reflector 45 10in the secondary light from the wavelength converter 4520 pass throughthe optical reflector 4530 and the light absorber 4540, and can beextracted to the exterior. Light components going toward thesemiconductor light emitting element 4132 in the secondary light fromthe wavelength converter 4520 are reflected by the first opticalreflector 4510, then pass through the optical reflector 4530 and thelight absorber 4540, and can be extracted to the exterior.

[0690] In a device Without the first optical reflector 45110, secondarylight emitted from the wavelength converter 4520 toward thesemiconductor light emitting element 4132 is absorbed or randomlyreflected by the semiconductor light emitting element 4132, and cannotbe extracted effectively. In contract, in the device according to theinvention, the first optical reflector 4510 reflects the secondary lightemitted from the wavelength converter 520 toward the semiconductor lightemitting element 4132, and makes it be extracted efficiently. That is,light is reciprocated between two optical reflectors until it iswavelength-converted. Therefore, most of light is finallywavelength-converted and extracted. Thus, the invention realizes ahighly efficient light emitting device having a high extractionefficiency.

[0691] Next explained are details of the semiconductor light emittingelement 4132 suitable for use in the invention to emit ultraviolet rays.

[0692]FIG. 137 is a schematic diagram showing a cross-sectional aspectof the semiconductor light emitting element 4132 suitable for use in theinvention. The semiconductor light emitting element 4132 used here is alight emitting diode (LED) for emission in the ultraviolet wavelengthband. As illustrated in FIG. 137, the semiconductor light emittingelement 4132 includes semiconductor layers 5002 through 5008 stacked ona sapphire substrate 5001. Metal organic chemical vapor deposition(MOCVD), for example, may be used for crystalline growth of thesesemiconductor layers. Appropriate thicknesses and growth temperatures ofrespective semiconductor layers are as follows. GaN buffer layer 50020.05 μm   550° C. n-GaN contact layer 5003 4.0 μm 1100° C. n-AlGaNcladding layer 5004 0.2 μm 1100° C. n-BGaN active layer 5005 0.5 μm1200° C. p-AlGaN first cladding layer 5006 0.05 μm  1100° C. p-AlGaNsecond cladding layer 5007 0.2 μm 1100° C. p-GaN contact layer 5008 0.05μm  1100° C.

[0693] Electrodes 5009 and 5010 for introducing electric current areformed on the n-GaN contact layer 5003 and p-GaN contact layer 5008,respectively. The semiconductor light emitting element 4132 is differentfrom conventional elements in using a gallium nitride compoundsemiconductor containing boron (B) as its active layer 5005 and usingAlGaN as layers adjacent to the active layer 5005. Development ofcrystals containing boron has been progressed mainly on BN. SiC was usedas the substrate crystal and a high crystalline growth temperature ashigh as approximately 1300° C. was required. However, for incorporatingB into GaN, there was the problem that B has a low solubility to GaNcrystal and a large lattice mismatch with SiC used as the substrate.Therefore, no BGaN tertiary mixed crystal with a high quality inflatness of the crystalline surface morphology, for example, could beobtained.

[0694] An excellent feature of the semiconductor light emitting element4132 shown here lies in promising growth of a high-quality BGaN crystalby using AlGaN containing Al highly resistant to heat as the underlyinglayer of GBaN. That is, even when the growth temperature is raised to1200° C. relatively high for growth of gallium nitride compounds afterAlGaN is grown under 1100° C., the surface of the crystal is maintainedsmooth, and growth of good-quality smooth BGaN crystal is ensured.

[0695] According to experiments by the Inventor, when the growthtemperature was raised further, surface roughness became apparentprobably due to dropping of N from the surface of AlGaN, and latticemismatching with AlGaN increased. That is, smoothness of the surface ofthe grown BGaN layer degraded. As the concentration of B increased.Smoothness of the crystal surface tended to degrade as the concentrationB increased, and the mixture ratio (X) of B in B_(x)Ga_(1-v)N crystalwith acceptably smooth surface was not higher than 0.1. Incorporation ofB into a mixed crystal with a higher concentration is still difficult.

[0696] However, the mixed crystal ratio the Inventor obtained wasconfirmed to be sufficient for a light emitting element for ultravioletbands and its wavelength was confirmed to be within 365 to 300 nm.

[0697] Another advantage of the structure shown here lies in that alight emitting portion containing BGaN can be grown on the relativelythick n-GaN contact layer 5003. In order to make the element structureshown in FIG. 137, it is necessary to expose the n-type contact layer5003 by etching the semiconductor layer upon making the n-side electrode5009. For example allowance in processing accuracy during the etchingprocess, the n-type contact layer 5003 is preferably grown relativelythick. However, BGaN mixed crystal is difficult to grow thick, and hencedegrades the production yield in the etching process. Therefore, BGaNmixed crystal is not suitable for use as the n-type contact layer.

[0698] BGaN mixed crystal has a mixture ratio of B which is in latticematching with a 6H-type SiC substrate. When it is grown on anelectrically conductive SiC substrate, the etching process for makingthe electrode is not necessary, and thick crystal need not be made.However, the crystalline grown itself is difficult because the ratio ofB in the mixed crystal is as high as 0.2, and the SiC substrate becomesopaque to wavelengths of ultraviolet rays. Therefore, it does not simplycontribute to improvements of element characteristics.

[0699] For the above-explained reasons, the structure of thesemiconductor light emitting element 4132 according to the invention, inwhich the BGaN light emitting layer is stacked on the GaN/AlGaN layers,facilitates growth of thick and smooth GaN/AlGaN layers without the needfor lattice matching conditions, and is very effective to realize LEDhaving BGaN as its light emitting layer.

[0700] Based on the structure shown in FIG. 137, a sample LED wasprepared by making a semiconductor multi-layered structure whichincludes a B_(x)Ga_(1-x)N active layer 5005 with the mixture ratio (X)of B being 0.05, p-A_(y)Ga_(1-y)N first cladding layer 5006 lath themixture ratio (Y) of Al being 0.3, n-Al_(z)Ga_(1-z)N cladding layer 1004and p-Al_(z)Ga_(1-z)N cladding layer 5007 with the mixture ratio (Z) ofAl being 0.2, and by processing it into chips of the size 350 μm×350 μm.As a result ultraviolet emission with emission spectral peaks ofapproximately 330 nm was obtained. The emission intensity responsive tothe driving current of 20 mA was approximately 10 μW.

[0701]FIG. 138 is a graph showing the relation between concentration ofsilicon and photoluminescence (PL) emission intensity when silicon (Si)is doped into BGaN. The abscissa indicates concentration of silicon inBGaN, and the ordinate indicates PL emission intensity in arbitraryunit. It is known from the graph that emission intensity of LED changeswith concentration of silicon. That is, as the concentration of siliconincreases, emission intensity suddenly increases from near 1E16 cm⁻³,maximizes near approximately 1E18 to 1E20 cm⁻³, and suddenly decreaseswith higher concentrations of silicon. According to the Inventor'sexperiment, even when the mixture ratio of B was changed, this tendencyof changes in emission intensity was the same. In the layer structureshown in FIG. 137, when silicon was doped into the BGaN active layer5005 by 1E19 cm⁻³, the emission wavelength remained 330 nm, and emissionintensity responsive to 20 mA was improved to approximately 2 mW. As aresult of an additional experiment by changing concentration of siliconin the active layer, concentrations of silicon ranging from 1E17 cm⁻³ to1E21 cm were confirmed to be practically appropriate for improvingcharacteristics and for making a stacked structure.

[0702]FIG. 139 is a diagram showing a schematic cross-sectional aspectof ultraviolet emission type semiconductor light emitting elementaccording to another embodiment of the invention. The semiconductorlight emitting element 4132B shown here has a multi-layered structuregrown on a 6H-type SiC substrate 5101. The semiconductor light emittingelement 4132B is substantially the same as the element explained withreference to Pig. 137 in thicknesses and growth temperatures ofrespective layers, but different therefrom in the GaN buffer layer 5102being doped with n-type impurities and in the n-side electrode 5109being formed on the bottom surface of the SiC substrate 5101. For growthof the crystals, metal organic chemical vapor deposition (MOCVD), forexample, may be used. As explained before, when the 6H-type SiCsubstrate 1101 is used, the element 4132B becomes opaque to light inultraviolet wavelength bands, and part of light radiated toward thesubstrate cannot be extracted to the exterior of the light emittingelement. However, since the effective lattice mismatch ratio of the6H-type SiC substrate with GaN is 3.4%, which is smaller than 13.8% of asapphire substrate, then density of dislocation and other variouscrystallographic defects caused by lattice mismatch can be decreased.Thus, the quality of the crystal layer underlying the BGaN active layer5105 is improved, which results in improving the crystallographicquality of the BGaN layer 5105 as well and in improving emissioncharacteristics of the light emitting element. That is, an advantage ofemployment of the 6H-type SiC substrate 5101 is an improvement ofemission characteristics by improvement of the crystalline property.

[0703] Based on the structure shown in FIG. 139, LED was prepared bymaking a multi-layered structure which includes a B_(x)Ga_(1-x)N activelayer 5105 with the mixture ratio (X) of B being 0.05, p-Al_(y)Ga_(1-y)Nfirst cladding layer 5106 with the mixture ratio (Y) of Al being 0.3,n-Al_(z)Ga_(1-z)N cladding layer 5104 and p-Al_(z)Ga_(1-z)N claddinglayer 5107 with the mixture ratio (Z) of Al being 0.2, and by processingit into chips of the size 350 μm×350 μm. As a result ultravioletemission with emission spectral peaks of approximately 330 nm wasobtained. With an element prepared by doping silicon into theB_(x)Ga_(1-x)N active layer 5105 so that the concentration of silicon inthe crystal be 1E19 cm⁻³, emission intensity responsive to the drivingcurrent of 20 mA was approximately 1.3 mW.

[0704]FIG. 140 is a cross-sectional schematic view showing a modifiedversion of the semiconductor light emitting element 4132B shown in FIG.139. In the semiconductor light emitting element 4132C shown here, then-side electrode 5109 is made by etching the semiconductor multi-layeredstructure of the semiconductor light emitting element 4132B from the topsurface to expose the n-GaN contact layer 5103. Here again, influencesgiven to the BGaN active layer important for element characteristics arethe same, and its usefulness is great.

[0705] Above-explained embodiments of the invention are not limited toillustrated structures or proposed manufacturing methods. Althoughexplanation has been made as using BGaN mixed crystal as the lightemitting layer, any BInAlGaN compound material may be used other thanBGaN tertiary compounds, as far as a heterojunction for confinement ofinjected carriers is formed.

[0706] Also the contact layer forming the p-side electrode is notlimited to the GaN layer, any material selected from InAlGaN compoundswill satisfy its characteristics, and materials having an absorptionloss to emission from the active layer will sufficiently satisfy thecharacteristics provided the layer is made thin. Moreover, althoughexplanation has been made on LED, the invention is applicable also togallium nitride compound semiconductor lasers (LDs).

[0707] Also in other respects, the invention can be modified or changedin various modes without departing from the concept of the invention.

[0708] Wile the present invention has been disclosed in terms of thepreferred embodiment in order to facilitate better understandingthereof, it should be appreciated that the invention can be embodied invarious ways Without departing from the principle of the invention.Therefore, the invention should be understood to include all possibleembodiments and modification to the show embodiments which can beembodied without departing from the principle of the invention as setforth in the appended claims.

What is claimed is:
 1. A semiconductor light emitting elementcomprising: a light emitting layer for emitting primary light having afirst wavelength; and a fluorescent material to absorb said primarylight emitted from said light emitting layer and to emit secondary lighthaving a second wavelength different from said first wavelength.
 2. Thesemiconductor light emitting element according to claim 1 furthercomprising: a first semiconductor layer having a first conduction type;and a second semiconductor layer having a second conduction type locatedon said first semiconductor layer, wherein said light emitting layer islocated between said first semiconductor layer and said secondsemiconductor layer.
 3. The semiconductor light emitting elementaccording to claim 2 wherein said fluorescent material is incorporatedin any of said first electrode and said second electrode.
 4. Thesemiconductor light emitting element according to claim 2 wherein saidfluorescent material is incorporated in any of said first semiconductorlayer, said light emitted layer and said second semiconductor layer. 5.The semiconductor light emitting element according to claim 2 whereinsaid fluorescent material is deposited on a surface of said lightemitting element.
 6. The semiconductor light emitting element accordingto claim 2 wherein said light emitting layer contains a gallium nitridecompound semiconductor and said second wavelength is longer than saidfirst wavelength.
 7. The semiconductor light emitting element accordingto claim 6 wherein said light emitting layer contains a gallium nitridecompound semiconductor including indium.
 8. The semiconductor lightemitting element according to claim 2 wherein said light emitting layercontains a material selected from the group consisting of ZnSe, ZnSe,ZnS, BN and SiC and said second wavelength is longer than said firstwavelength.
 9. The semiconductor light emitting element according toclaim 2 wherein said first wavelength is not longer than 380 nm.
 10. Asemiconductor light emitting device comprising: a packaging member; anda semiconductor light emitting element mounted on said packaging member,said semiconductor light emitting element inluding a first semiconductorlayer of a first conduction type, a light emitting layer located on saidfirst semiconductor layer for emitting primary light having a firstwavelength, a second semiconductor layer of a second conduction type anda fluorescent material to absorb said primary light emitted from saidlight emitting layer and to emit secondary light having a secondwavelength different from said first wavelength.
 11. The semiconductorlight emitting device according to claim 10 wherein said packagingmember is a selected one from the group consisting of lead frame, stemand substrate.
 12. A semiconductor light emitting device comprising: apackaging member; a semiconductor light emitting element packaged onsaid packaging member to emit primary light having a first wavelength;and a wavelength converter located on a surface of said light emittingelement and including a fluorescent material to absorb said primarylight emitted from said light emitting element and to emit secondarylight having a second wavelength different from said first wavelength.13. The semiconductor light emitting device according to claim 12wherein said wavelength converter contains an adhesive medium dispersedwith said fluorescent material.
 14. The semiconductor light emittingdevice according to claim 12 wherein said wavelength converter containsa medium dispersed with said fluorescent material, said mediumcontaining a selected one from the group consisting of an inorganicpolymer, a rubber material, a farinaceous material and a protein as amain component.
 15. The semiconductor light emitting device according toclaim 12 wherein said wavelength converter includes a layer of a mediumcontaining a selected one from the group consisting of an inorganicpolymer, a rubber organic material, a farinaceous material and a proteinas a main component, and said wavelength converter includes a layer ofsaid fluorescent material stacked on said layer of a medium.
 16. Thesemiconductor light emitting device according to claim 12 wherein therefractivity of said wavelength converter is between the refractivity ofa light emitting part of said light emitting element and therefractivity of an adjacent part through where said secondary light isemitted.
 17. A semiconductor light emitting device comprising: apackaging member; a semiconductor light emitting element packaged onsaid packaging member to emit primary light having a first wavelength;and a resin molded so that said light emitting element is covered,wherein said resin contains a fluorescent material in its surface regionto absorb said primary light emitted from said light emitting elementand to emit secondary light having a second wavelength different fromsaid first wavelength.
 18. The semiconductor light emitting deviceaccording to claim 17 wherein said packaging member is a selected onefrom the group consisting of lead frame, stem and substrate.
 19. Asemiconductor light emitting device comprising: a packaging member; asemiconductor light emitting element packaged on said packaging memberto emit primary light having a first wavelength; a resin molded so thatsaid light emitting element is covered; and a wavelength converterstacked on said resin, wherein said wavelength converter contains afluorescent material to absorb said primary light emitted from saidlight emitting element and to emit secondary light having a secondwavelength different from said first wavelength.
 20. The semiconductorlight emitting device according to claim 19 wherein said packagingmember is a selected one from the group consisting of lead frame, stemand substrate.
 21. A semiconductor light emitting device comprising: apackaging member; a semiconductor light emitting element packaged onsaid packaging member to emit primary light having a first wavelength;and a fluorescent material absorbing said primary light emitted fromsaid light emitting element and emitting secondary light having a secondwavelength different from said first wavelength.
 22. The semiconductorlight emitting device according to claim 21 further comprising a resinmolded so that said light emitting element is covered, wherein saidresin has a cavity in its inside, said light emitting element is placedin said cavity, and said fluorescent material is deposited on a innerwall of said cavity.
 23. The semiconductor light emitting deviceaccording to claim 21 further comprising a first resin formed so thatsaid light emitting element is covered and a second resin formed so thatsaid first resin is covered, wherein said first resin contains saidfluorescent material.
 24. The semiconductor light emitting deviceaccording to claim 23 wherein said first resin is a dipping resin andsaid second resin is a molded resin.
 25. The semiconductor lightemitting device according to claim 21 wherein said packaging membercontains said fluorescent material.
 26. The semiconductor light emittingdevice according to claim 21 further comprising an adhesive fixing saidlight emitting element to said packaging member, wherein said adhesivecontains said fluorescent material.
 27. The semiconductor light emittingdevice according to claim 21 further comprising a wavelength converterstacked on said packaging member, wherein said wavelength convertercontains said fluorescent material.
 28. The semiconductor light emittingdevice according to claim 21 further comprising a reflector reflecting alight and a wavelength converter stacked on said reflector, wherein saidwavelength converter contains said fluorescent material.
 29. Thesemiconductor light emitting device according to claim 21 furthercomprising a film layer to receive said primary light emitted from saidlight emitting element, wherein said film layer contains saidfluorescent material.
 30. The semiconductor light emitting deviceaccording to claim 21 further comprising a cap located to cover saidlight emitting element and a wavelength converter located on the lightextraction part of said cap, wherein said wavelength converter containssaid fluorescent material.
 31. The semiconductor light emitting deviceaccording to claim 21 further comprising a lens to converge a lightemitted from said light emitting element, wherein said lens containssaid fluorescent material in its inside or on its surface.
 32. Thesemiconductor light emitting element according to claim 21 wherein saidlight emitting element has a light emitting layer containing a galliumnitride compound semiconductor, and said second wavelength is longerthan said first wavelength.
 33. The semiconductor light emitting elementaccording to claim 21 wherein said light emitting element has a lightemitting layer made of a material selected from the group consisting ofZnSe, ZnSSe, ZnS, BN and SiC, and said second wavelength is longer thansaid first wavelength.
 34. The semiconductor light emitting elementaccording to claim 21 wherein said first wavelength is not longer than380 nm.
 35. The semiconductor light emitting element according to claim21 wherein said secondary light is a visible light.
 36. Thesemiconductor light emitting element according to claim 21 wherein saidsecondary light has at least three wavelength peaks each of whichsubstantially corresponds to red, green and blue, respectively.
 37. Amethod for making a semiconductor light emitting device, comprising thesteps of: mounting a semiconductor light emitting element on a packagingmember; coating an adhesive medium on said light emitting element;scattering a fluorescent material on said medium; and hardening saidmedium.
 38. The method according to claim 37 wherein said mediumcontains a selected one from the group consisting of an inorganicpolymer, a rubber material, a farinaceous material and a protein as amain component.
 39. A method for making a semiconductor light emittingdevice, comprising the steps of: mounting a semiconductor light emittingelement on a packaging member; coating an adhesive medium dispersed Witha fluorescent material on said light emitting element; and hardeningsaid medium.
 40. The method according to claim 39 wherein said mediumcontains a selected one from the group consisting of an inorganicpolymer, a rubber material, a farinaceous material and a protein as amain component.
 41. A semiconductor light emitting element comprising: alight emitting layer for emitting primary light having a firstwavelength; a wavelength converter located in the light extraction sideof said light emitting layer to absorb said primary light emitted fromsaid light emitting layer and to emit secondary light having a secondwavelength different from said first wavelength; and a light absorberlocated in the light extraction side of said wavelength converter, andhaving a low absorptance to said secondary light emitted from saidwavelength converter and a high absorptance to said primary lightemitted from said light emitting layer.
 42. The semiconductor lightemitting element according to claim 41 wherein said light emitting layercontains as its major component a material selected from the groupconsisting of gallium nitride compound semiconductors, ZnSe, ZnS, ZnSSe,SiC and BN, said first wavelength is not longer than 380 nm, saidwavelength converter contains a fluorescent material, and said secondarylight is a visible light.
 43. A semiconductor light emitting elementcomprising: a light emitting layer for emitting primary light having afirst wavelength; a wavelength converter located in the light extractionside of said light emitting layer to absorb said primary light emittedfrom said light emitting layer and to emit secondary light having asecond wavelength different from said first wavelength; and a firstoptical reflector located in the light extraction side of saidwavelength converter, and having a low reflectance to said secondarylight emitted from said wavelength converter and a high reflectance tosaid primary light emitted from said light emitting layer.
 44. Thesemiconductor light emitting element according to claim 43 wherein saidlight emitting layer contains as its major component a material selectedfrom the group consisting of gallium nitride compound semiconductors,ZnSe, ZnS, ZnSSe, SiC and BN, said first wavelength is not longer than380 nm, said wavelength converter contains a fluorescent material, andsaid secondary light is a visible light.
 45. The semiconductor lightemitting element according to one of claim 43 further comprising a lightabsorber located in the light extraction side of said wavelengthconverter, and having a low absorptance to said secondary light emittedfrom said wavelength converter and a high absorptance to said primarylight emitted from said light emitting layer.
 46. The semiconductoremitting element according to claim 45 wherein said first opticalreflector is located between said light emitting layer and said lightabsorber.
 47. A semiconductor light emitting element comprising: a lightemitting layer for emitting primary light having a first wavelength; awavelength converter located in the light extraction side of said lightemitting layer to absorb said primary light emitted from said lightemitting layer and to emit secondary light having a second wavelengthdifferent from said first wavelength; and a second optical reflectorlocated on one side of said light emitting layer opposite from the lightextraction side to reflect said primary light.
 48. The semiconductorlight emitting element according to claim 47 wherein said light emittinglayer contains as its major component a material selected from the groupconsisting of gallium nitride compound semiconductors, ZnSe, ZnS, ZnSSe,SiC and BN, said first wavelength is not longer than 380 nm, saidwavelength converter contains a fluorescent material, and said secondarylight is a visible light.
 49. The semiconductor light emitting elementaccording to one of claim 47 further comprising a light absorber locatedin the light extraction side of said wavelength converter, and having alow absorptance to said secondary light emitted from said wavelengthconverter and a high absorptance to said primary light emitted from saidlight emitting layer.
 50. The semiconductor light emitting elementaccording to claim 47 further comprising a first optical reflectorlocated in the light extraction side of said wavelength converter, andhaving a low reflectance to said secondary light emitted from saidwavelength converter and a high reflectance to said primary lightemitted from said light emitting layer.
 51. A semiconductor lightemitting element comprising: a light emitting layer for emitting primarylight having a first wavelength; a wavelength converter located in thelight extraction side of said light emitting layer to absorb saidprimary light emitted from said light emitting layer and to emitsecondary light having a second wavelength different from said firstwavelength; and a third optical reflector configured to enclose saidlight emitting layer except the light extraction part to reflect saidprimary light emitted from said light emitting layer.
 52. Thesemiconductor light emitting element according to claim 51 wherein saidlight emitting layer contains as its major component a material selectedfrom the group consisting of gallium nitride compound semiconductors,ZnSe, ZnS, ZnSSe, SiC and BN, said first wavelength is not longer than380 nm, said wavelength converter contains a fluorescent material, andsaid secondary light is a visible light.
 53. The semiconductor lightemitting element according to one of claim 51 further comprising a lightabsorber located in the light extraction side of said wavelengthconverter, and having a low absorptance to said secondary light emittedfrom said wavelength converter and a high absorptance to said primarylight emitted from said light emitting layer.
 54. The semiconductorlight emitting element according to claim 51 further comprising a firstoptical reflector located in the light extraction side of saidwavelength converter, and having a low reflectance to said secondarylight emitted from said wavelength converter and a high reflectance tosaid primary light emitted from said light emitting layer.
 55. Asemiconductor light emitting element comprising: a light emitting layerfor emitting primary light having a first wavelength; a wavelengthconverter located in the light extraction side of said light emittinglayer to absorb said primary light emitted from said light emittinglayer and to emit secondary light having a second wavelength differentfrom said first wavelength; and a fourth optical reflector locatedbetween said light emitting layer and said wavelength converter, andhaving a low reflectance to said primary light and a high reflectance tosaid secondary light.
 56. The semiconductor light emitting elementaccording to claim 55 wherein said light emitting layer contains as itsmajor component a material selected from the group consisting of galliumnitride compound semiconductors, ZnSe, ZnS, ZnSSe, SiC and BN, saidfirst wavelength is not longer than 380 nm, said wavelength convertercontains a fluorescent material, and said secondary light is a visiblelight.
 57. The semiconductor light emitting element according to one ofclaim 55 further comprising a light absorber located in the lightextraction side of said wavelength converter, and having a lowabsorptance to said secondary light emitted from said wavelengthconverter and a high absorptance to said primary light emitted from saidlight emitting layer.
 58. The semiconductor light emitting elementaccording to claim 55 further comprising a first optical reflectorlocated in the light extraction side of said wavelength converter, andhaving a low reflectance to said secondary light emitted from saidwavelength converter and a high reflectance to said primary lightemitted from said light emitting layer.
 59. A semiconductor lightemitting device comprising: a packaging member; a semiconductor lightemitting element packaged on said packaging member to emit primary lighthaving a first wavelength; a wavelength converter located in the lightextraction side of said light emitting element to absorb said primarylight emitted from said light emitting element and to emit secondarylight having a second wavelength different from said first wavelength;and a light absorber located in the light extraction side of saidwavelength converter, and having a low absorptance to said secondarylight emitted from said wavelength converter and a high absorptance tosaid primary light emitted from said light emitting element.
 60. Thesemiconductor light emitting device according to claim 59 wherein saidlight emitting element contains in its light emitting layer a materialselected from the group consisting of gallium nitride compoundsemiconductors, ZnSe, ZnS, ZnSSe, SiC and BN, said first wavelength isnot longer than 380 nm, said wavelength converter contains a fluorescentmaterial, and said secondary light is a visible light.
 61. Asemiconductor light emitting device comprising: a packaging member; asemiconductor light emitting element packaged on said packaging memberto emit primary light having a first wavelength; a wavelength converterlocated in the light extraction side of said light emitting element toabsorb said primary light emitted from said light emitting element andto emit secondary light having a second wavelength different from saidfirst wavelength; and a first optical reflector located in the lightextraction side of said wavelength converter, and having a lowreflectance to said secondary light emitted from said wavelengthconverter and a high reflectance to said primary light emitted from saidlight emitting element.
 62. The semiconductor light emitting deviceaccording to claim 61 wherein said light emitting element contains inits light emitting layer a material selected from the group consistingof gallium nitride compound semiconductors, ZnSe, ZnS, ZnSSe, SiC andBN, said first wavelength is not longer than 380 nm, said wavelengthconverter contains a fluorescent material, and said secondary light is avisible light.
 63. The semiconductor light emitting device according toclaim 61 further comprising a light absorber located in the lightextraction side of said wavelength converter, and having a lowabsorptance to said secondary light emitted from said wavelengthconverter and a high absorptance to said primary light emitted from saidlight emitting element.
 64. The semiconductor light emitting deviceaccording to claim 63 wherein said first optical reflector is locatedbetween said light emitting element and said light absorber.
 65. Asemiconductor light emitting device comprising: a packaging member; asemiconductor light emitting element packaged on said packaging memberto emit primary light having a first wavelength; a wavelength converterlocated in the light extraction side of said light emitting element toabsorb said primary light emitted from said light emitting element andto emit secondary light having a second wavelength different from saidfirst wavelength; and a second optical reflector located on one side ofsaid light emitting element opposite from the light extraction side toreflect said primary light.
 66. The semiconductor light emitting deviceaccording to claim 65 wherein said light emitting element contains inits light emitting layer a material selected from the group consistingof gallium nitride compound semiconductors, ZnSe, ZnS, ZnSSe, SiC andBN, said first wavelength is not longer than 380 nm, said wavelengthconverter contains a fluorescent material, and said secondary light is avisible light.
 67. The semiconductor light emitting device according toclaim 65 further comprising a light absorber located in the lightextraction side of said wavelength converter, and having a lowabsorptance to said secondary light emitted from said wavelengthconverter and a high absorptance to said primary light emitted from saidlight emitting element.
 68. The semiconductor light emitting deviceaccording to claim 65 further comprising a first optical reflectorlocated in the light extraction side of said wavelength converter, andhaving a low reflectance to said secondary light emitted from saidwavelength converter and a high reflectance to said primary lightemitted from said light emitting element.
 69. A semiconductor lightemitting device comprising: a packaging member; a semiconductor lightemitting element packaged on said packaging member to emit primary lighthaving a first wavelength; a wavelength converter located in the lightextraction side of said light emitting element to absorb said primarylight emitted from said light emitting element and to emit secondarylight having a second wavelength different from said first wavelength;and a third optical reflector configured to enclose said light emittingelement except the light extraction part to reflect said primary lightemitted from said light emitting element.
 70. The semiconductor lightemitting device according to claim 69 wherein said light emittingelement contains in its light emitting layer a material selected fromthe group consisting of gallium nitride compound semiconductors, ZnSe,ZnS, ZnSSe, SiC and BN, said first wavelength is not longer than 380 nm,said wavelength converter contains a fluorescent material, and saidsecondary light is a visible light.
 71. The semiconductor light emittingdevice according to claim 69 further comprising a light absorber locatedin the light extraction side of said wavelength converter, and having alow absorptance to said secondary light emitted from said wavelengthconverter and a high absorptance to said primary light emitted from saidlight emitting element.
 72. The semiconductor light emitting deviceaccording to claim 69 further comprising a first optical reflectorlocated in the light extraction side of said wavelength converter, andhaving a low reflectance to said secondary light emitted from saidwavelength converter and a high reflectance to said primary lightemitted from said light emitting element.
 73. A semiconductor lightemitting device comprising: a packaging member; a semiconductor lightemitting element packaged on said packaging member to emit primary lighthaving a first wavelength; a wavelength converter located in the lightextraction side of said light emitting element to absorb said primarylight emitted from said light emitting element and to emit secondarylight having a second wavelength different from said first wavelength;and a fourth optical reflector located between said light emittingelement and said wavelength converter, and having a low reflectance tosaid primary light and a high reflectance to said secondary light. 74.The semiconductor light emitting device according to claim 73 whereinsaid light emitting element contains in its light emitting layer amaterial selected from the group consisting of gallium nitride compoundsemiconductors, ZnSe, ZnS, ZnSSe, SiC and BN, said first wavelength isnot longer than 380 nm, said wavelength converter contains a fluorescentmaterial, and said secondary light is a visible light.
 75. Thesemiconductor light emitting device according to claim 73 furthercomprising a light absorber located in the light extraction side of saidwavelength converter, and having a low absorptance to said secondarylight emitted from said wavelength converter and a high absorptance tosaid primary light emitted from said light emitting element.
 76. Thesemiconductor light emitting device according to claim 73 furthercomprising a first optical reflector located in the light extractionside of said wavelength converter, and having a low reflectance to saidsecondary light emitted from said wavelength converter and a highreflectance to said primary light emitted from said light emittingelement.
 77. An image display device comprising: a semiconductor lightemitting element for emitting primary light having a first wavelength; aluminance adjuster for adjusting intensity of said primary light emittedfrom said semiconductor light emitting element; a wavelength converterfor absorbing said primary light adjusted in intensity by said luminanceadjuster and for emitting secondary light having a second wavelengthdifferent from said first wavelength; and a first optical reflectorlocated in the light extraction side of said wavelength converter, andhaving a low reflectance to said secondary light emitted from saidwavelength converter and a high reflectance to said primary lightemitted from said light emitting element.
 78. The image display deviceaccording to claims 77 further comprising a light absorber located onthe light extraction side of said first optical reflector, and having alow absorptance to said secondary light passing through said firstoptical reflector and a high absorptance to said primary light passingthrough said first optical reflector.
 79. The image display deviceaccording to claim 77 further comprising a fourth optical reflectorlocated between said semiconductor light emitting element and saidwavelength converter, and having a low reflectance to said primary lightand a high reflectance to said secondary light.
 80. The image displaydevice according to claim 77 wherein said light emitting elementcontains in its light emitting layer a material selected from the groupconsisting of gallium nitride compound semiconductors, ZnSe, ZnS, ZnSSe,SiC and BN, said first wavelength is not longer than 380 nm, saidwavelength converter contains a fluorescent material, and said secondarylight is a visible light.
 81. An image display device comprising: asemiconductor light emitting element for emitting primary light having afirst wavelength; a wavelength converter for absorbing said primarylight emitted from said semiconductor light emitting element and forreleasing secondary light having a second wavelength different from saidfirst wavelength; a first optical reflector located in the lightextraction side of said wavelength converter, and having a lowreflectance to said secondary light released from said wavelengthconverter and a high reflectance to said primary light emitted from saidlight emitting element; and a luminance adjuster for adjusting intensityof said secondary light passing through said first optical reflector.82. The image display device according to claims 81 further comprising alight absorber located on the light extraction side of said firstoptical reflector, and having a low absorptance to said secondary lightpassing through said first optical reflector and a high absorptance tosaid primary light passing through said first optical reflector.
 83. Theimage display device according to claim 81 further comprising a fourthoptical reflector located between said semiconductor light emittingelement and said wavelength converter, and having a low reflectance tosaid primary light and a high reflectance to said secondary light. 84.The image display device according to claim 81 wherein said lightemitting element contains in its light emitting layer a materialselected from the group consisting of gallium nitride compoundsemiconductors, ZnSe, ZnS, ZnSSe, SiC and BN, said first wavelength isnot longer than 380 nm, said wavelength converter contains a fluorescentmaterial, and said secondary light is a visible light.